adrot.dll Not Found: Safe Fixes for Legacy IIS on Windows

adrot.dll is a Microsoft IIS component used by the classic ASP MSWC.AdRotator COM object. If adrot.dll is missing or cannot be loaded, the safest fix is usually to repair the legacy IIS installation or application that calls it, not to download a replacement DLL.

This file is not a normal Windows desktop dependency, Visual C++ runtime, DirectX file, or .NET assembly. It belongs to the old Internet Information Services advertising component, so the correct repair depends on whether the computer is running an IIS application, a migrated Classic ASP site, or an unrelated program that is incorrectly requesting the file.

As an Amazon Associate I earn from qualifying purchases.

What adrot.dll does

Microsoft documents MSWC.AdRotator as a Classic ASP component that reads an advertisement rotation schedule and returns advertisement HTML. A typical ASP page creates it like this:

Set objLoad = Server.CreateObject("MSWC.AdRotator")
GetAd = objLoad.GetAdvertisement("MyAdRot.txt")

The component is implemented as a native COM DLL, not as a managed .NET assembly. Microsoft’s historical IIS documentation identifies the component as part of IIS and associates it with the adrot.dll file.

Microsoft file information confirms an x86 Windows Server 2003 SP2 IIS copy with these details:

• File: Adrot.dll
• Version: 6.0.3790.3959
• Size: 58,880 bytes
• Platform: x86

That is historical evidence, not a universal version that should be copied onto every modern Windows installation. Current Windows 10, Windows 11, and current Windows Server installations should not be assumed to include this legacy component.

First identify the type of error

The repair path differs depending on what is reporting the problem.

Windows loader error

These messages usually indicate that an executable or service tried to load the file:

• “The program can’t start because adrot.dll is missing from your computer.”
• “Error loading adrot.dll. The specified module could not be found.”
• “adrot.dll could not be loaded”
• “adrot.dll is corrupted”

The calling program may be an IIS-related service, an old installer, a scheduled task, or an unrelated application that has retained an obsolete dependency.

Classic ASP or COM activation error

A web application may instead fail at:

Server.CreateObject("MSWC.AdRotator")

Commonly reported variants include ASP 0177 : 800401f3, “Runtime Error – adrot.dll,” or a general COM activation failure.

In this situation, the file may exist but still fail because:

• the DLL is not registered;
• the wrong 32-bit or 64-bit registry view was used;
• the IIS application pool is running with the wrong architecture;
• Classic ASP is not installed;
• the IIS version does not provide the old component;
• a dependency of the DLL is missing.

Do not treat every COM activation error as proof that the file itself is absent.

Fix 1: Confirm that the application really needs adrot.dll

Time needed: 5 to 15 minutes

Before changing Windows, identify the program or website generating the error.

For an IIS server

1. Open IIS Manager.
2. Expand the server name and select Sites.
3. Identify the site that fails.
4. Check whether it contains .asp pages, especially pages using Server.CreateObject.
5. Search the site’s application files for:
   text
MSWC.AdRotator
6. Check the IIS logs and Windows Event Viewer for the failing URL or application pool.

If the site does not use Classic ASP or MSWC.AdRotator, the error may come from a separate startup item, scheduled task, or service.

For a desktop error

1. Note the exact program name shown in the error.
2. Open Task Manager with Ctrl+Shift+Esc.
3. Select Startup apps and look for entries related to the program.
4. Open Task Scheduler by pressing Win+R, typing taskschd.msc, and pressing Enter.
5. Review tasks under Task Scheduler Library for the same program or vendor.
6. Check Settings → Apps → Installed apps for the application that triggers the message.

Do not install IIS merely because a desktop program mentions adrot.dll. The calling process must be identified first.

Fix 2: Install Classic ASP and required IIS features

Time needed: 10 to 20 minutes

Classic ASP is an optional IIS feature. It is not installed automatically on every Windows system, and installing it does not prove that the old MSWC.AdRotator component is included.

Windows 10 or Windows 11

1. Press Win+R.
2. Type:
   text
optionalfeatures
3. Press Enter.
4. Expand Internet Information Services.
5. Expand World Wide Web Services.
6. Expand Application Development Features.
7. Select ASP.
8. Also select ISAPI Extensions if it is not already enabled.
9. Select OK.
10. Allow Windows to complete the installation.
11. Restart IIS from an elevated Command Prompt:
    cmd
iisreset

Microsoft’s documented feature path is Control Panel → Programs and Features → Turn Windows features on or off → Internet Information Services → World Wide Web Services → Application Development Features → ASP.

Windows Server

1. Open Server Manager.
2. Select Manage → Add Roles and Features.
3. Choose Role-based or feature-based installation.
4. Select the server.
5. Expand Web Server (IIS).
6. Expand Web Server.
7. Expand Application Development.
8. Select ASP.
9. Select ISAPI Extensions if required.
10. Complete the wizard.
11. Restart IIS:
    cmd
iisreset

Test the ASP page again after installation.

If the site now processes Classic ASP but still reports that MSWC.AdRotator cannot be created, the ASP hosting feature is working and the remaining problem is the legacy COM component, registration, architecture, or IIS-version compatibility.

Fix 3: Check 32-bit IIS application-pool settings

Time needed: 10 to 20 minutes

The confirmed Microsoft file evidence for this component is x86. On a 64-bit server, a 32-bit COM DLL must be registered in the 32-bit registry view and loaded by a compatible worker process.

1. Open IIS Manager.
2. Select the server name.
3. Select Application Pools.
4. Find the pool used by the failing site.
5. Right-click it and select Advanced Settings.
6. Find Enable 32-Bit Applications.
7. Set it to True if the application is known to be 32-bit.
8. Select OK.
9. Right-click the application pool and select Recycle.
10. Test the ASP application again.

Do not enable 32-bit mode automatically for every IIS site. Confirm that the application and its other COM components are 32-bit before changing the pool.

A 32-bit DLL should not be copied into a random folder or treated as a 64-bit system file. Historical IIS installations commonly used a path under:

%windir%System32inetsrv

On 64-bit Windows, directory and registry redirection make architecture important. The name System32 does not by itself mean that a particular DLL is 64-bit.

Fix 4: Restore the file from a trusted IIS or Windows source

Time needed: 20 minutes to several hours

If the application genuinely requires MSWC.AdRotator, determine whether the file was deleted, quarantined, damaged, or never included in the destination IIS installation.

Check antivirus quarantine

1. Open Windows Security.
2. Select Virus & threat protection.
3. Select Protection history.
4. Look for an event involving adrot.dll.
5. Do not restore it solely because the filename is familiar.
6. Restore it only if it came from a trusted system installation or verified backup and the file is identified as a legitimate Microsoft binary.
7. Run a full security scan after restoration.

Check a known-good server or backup

Use a matching, licensed IIS or Windows installation, original installation media, an official servicing package, or a known-good system backup. The source should match the operating-system generation, IIS generation, architecture, and patch level as closely as possible.

Do not assume that the documented Windows Server 2003 x86 file is correct for Windows 10, Windows 11, or a newer Windows Server release. It is not a universal replacement.

After restoring a legitimate copy, register it only if the IIS application uses it as a COM server and registration is required.

Fix 5: Register the COM DLL with the correct regsvr32

Time needed: 5 to 15 minutes

MSWC.AdRotator is a native COM component, so regsvr32 can be relevant. This is different from ordinary runtime DLL repair. regsvr32 should not be used indiscriminately on Visual C++ runtime files, DirectX files, .NET assemblies, or arbitrary DLLs.

First locate the trusted file. Then open Command Prompt as administrator.

For a 32-bit DLL on 64-bit Windows, use the 32-bit copy of regsvr32:

%windir%SysWOW64regsvr32.exe "C:pathtoadrot.dll"

For a 64-bit DLL, the usual 64-bit registration tool is:

%windir%System32regsvr32.exe "C:pathtoadrot.dll"

The directory names are counterintuitive on 64-bit Windows: SysWOW64 contains 32-bit system tools, while System32 contains 64-bit system tools.

A successful registration normally produces a confirmation dialog. Recycle the IIS application pool and test the application.

If registration fails, record the exact message. Possible causes include:

• the file is not a valid COM server;
• the file is damaged;
• a dependency is missing;
• the wrong regsvr32 architecture was used;
• the DLL does not expose the expected registration entry point;
• the component is not supported by the installed IIS version.

Do not repeatedly register random copies until one appears to work. That can leave multiple conflicting registrations and obscure the original problem.

Fix 6: Repair Windows component files with DISM and SFC

Time needed: 20 to 45 minutes, plus restart time

Use these commands when the DLL belongs to the Windows installation and you suspect component-store corruption. They cannot create a legacy component that the current Windows version never shipped.

1. Open Start.
2. Type Command Prompt.
3. Right-click Command Prompt.
4. Select Run as administrator.
5. Run:
   cmd
DISM.exe /Online /Cleanup-Image /RestoreHealth
6. Wait for it to finish.
7. Then run:
   cmd
sfc /scannow
8. Restart Windows.
9. Test the application or IIS site again.

If SFC reports that it repaired files, restart and retest. If it reports that it could not repair some files, run DISM again, restart, and repeat SFC once.

When manually repeating DISM and SFC becomes difficult to track, Outbyte PC Repair can scan for system problems and show what needs attention; its free scan identifies issues, while repair features require the full version. It is optional, and it does not replace restoring the correct IIS component or migrating unsupported Classic ASP code.

A successful SFC run does not prove that adrot.dll is available. SFC repairs protected files belonging to the installed Windows image. It will not restore a component that was never part of that Windows release.

Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Support on Ko-Fi

Fix 7: Update or reinstall the calling program and its drivers

Time needed: 15 to 45 minutes

This step applies when the error comes from a desktop application, service, or hardware-related package rather than an IIS website.

1. Open Settings.
2. Select Apps → Installed apps.
3. Find the program named in the error.
4. Select the three-dot menu.
5. Choose Uninstall or Advanced options if a repair option is available.
6. Restart Windows.
7. Install the latest version from the software vendor’s official source.

For a driver-related application:

1. Right-click Start.
2. Select Device Manager.
3. Expand the relevant device category.
4. Right-click the device.
5. Select Update driver.
6. Choose Search automatically for drivers.
7. If that does not help, select Uninstall device.
8. Restart Windows.
9. Install the driver supplied by the device manufacturer.

Outbyte Driver Updater can reduce the manual work of hunting through multiple driver versions; its free scan identifies outdated drivers, while driver installation requires the full version. It is optional, and a driver update is not the correct remedy when an IIS migration lacks the legacy Ad Rotator component.

If the application is specifically an old Classic ASP site, reinstalling a desktop program or driver is unlikely to help. Repair the IIS deployment or replace the obsolete component instead.

Fix 8: Migrate away from MSWC.AdRotator

Time needed: Several hours to several days

This is the safest long-term solution when the application has moved from IIS 6 to IIS 7 or later and the destination server does not provide the old component.

Replace the MSWC.AdRotator call with application code that:

• reads advertisement data from a database or controlled configuration file;
• selects an advertisement using supported ASP logic;
• emits validated HTML;
• records clicks and rotation state using the application’s existing data layer.

Alternatively, retain the application in a correctly maintained legacy-compatible environment while a migration is planned. Do not expose an old IIS server directly to the internet simply to preserve one component.

Installing Classic ASP may allow old .asp pages to run, but it does not automatically install MSWC.AdRotator. Treat the hosting feature and the obsolete COM component as separate dependencies.

Why adrot.dll errors happen

Likely cause	What it means	Correct direction
IIS 6 application migrated to newer IIS	The destination may not include the old Ad Rotator component	Migrate the advertisement code
Wrong architecture	x86 COM registration or worker-process settings do not match	Use the matching 32-bit registration view and application pool
File deleted or quarantined	The original server component is gone	Restore from trusted IIS media or backup
Classic ASP is missing	IIS cannot host the ASP application correctly	Install ASP and required ISAPI features
COM registration is missing	The file exists but cannot activate	Register the trusted DLL with the correct regsvr32
Dependency is missing	“Specified module could not be found” may refer to a dependency	Check architecture, dependencies, and application logs
Windows corruption	Protected system files may be damaged	Run DISM and SFC conditionally
Unrelated startup program	A non-IIS process is requesting the file	Identify, repair, or remove the calling program

Why random DLL downloads are unsafe

Downloading adrot.dll from an unofficial DLL site can provide:

• the wrong IIS generation;
• the wrong architecture;
• a modified or damaged binary;
• a file that is not registered;
• a file with dependencies that are still missing.

It can also hide the actual problem, especially when the destination server never supported MSWC.AdRotator. There is no verified current standalone Microsoft redistributable download for this component.

Use Microsoft IIS documentation, matching Windows or IIS installation media, official servicing packages, and known-good system backups instead. Never replace a system or IIS file simply because its filename matches the error.

Verification checklist

After making a repair, confirm each applicable item:

• The failing process or IIS site has been identified.
• The application actually uses MSWC.AdRotator, or the unrelated caller has been found.
• Classic ASP is installed where required.
• ISAPI Extensions are enabled where required.
• The DLL architecture matches the application.
• The IIS application pool uses 32-bit mode when required.
• The file came from a trusted, matching source.
• Registration used the correct regsvr32 architecture.
• The application pool or IIS service was restarted.
• Event Viewer and IIS logs show no new COM activation errors.
• The application no longer reports a loader or Server.CreateObject failure.

Frequently asked questions

Is adrot.dll a Windows system file?

It is a genuine Microsoft IIS component, but it is a legacy one. Do not assume that every current Windows installation contains it.

Is adrot.dll part of Classic ASP?

It is associated with the Classic ASP MSWC.AdRotator component. Installing Classic ASP enables ASP hosting but does not guarantee that the old Ad Rotator COM server is installed.

Is adrot.dll 32-bit or 64-bit?

The strongest verified Microsoft file evidence identifies an x86 copy. Treat the component as 32-bit unless you have authoritative information for the exact IIS installation involved.

Should I copy it into System32?

No. Manual copying can create architecture, registration, and version problems. Restore it only from a matching trusted source, then configure IIS and COM registration correctly.

Should I run regsvr32 on adrot.dll?

It can be appropriate because MSWC.AdRotator is a native COM component. Use it only with a trusted file and the correct 32-bit or 64-bit registration tool. It is not a general DLL repair command.

Can SFC restore adrot.dll?

Only if the file belongs to the installed Windows component set and is protected by that installation. SFC cannot add an obsolete IIS component that the operating system never shipped.

Why does ASP 0177 appear when the file exists?

The COM class may be unregistered, registered in the wrong registry view, incompatible with the worker process, missing a dependency, or unsupported by the IIS version.

What is the best fix after an IIS migration?

Replace MSWC.AdRotator with supported application code. Restoring the old component may provide short-term compatibility, but migration removes the dependency and is usually the safer long-term path.

Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.