radcui.dll is a legitimate Microsoft Windows system file used by the RemoteApp and Desktop Connections subsystem, not a Visual C++ or game runtime. If Windows says it is missing or damaged, repair Windows first rather than downloading a replacement DLL.
What this file actually does
The filename refers to RemoteApp and Desktop Connection UI Component. It supports the Windows interface and component functions associated with RemoteApp and Desktop Connections, a Windows feature used to publish remote applications and desktops.
It is related to the Windows Remote Desktop client, but it is not the same thing as mstsc.exe, the executable commonly used to open a standard Remote Desktop session. Microsoft describes Remote Desktop Connection as including the RemoteApp and Desktop Connections Control Panel applet and related functionality. Microsoft’s Remote Desktop client documentation explains that relationship.
A genuine copy is published by Microsoft Corporation and belongs to the Microsoft Windows Operating System. Its normal locations are:
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C:WindowsSystem32RADCUI.dllfor the 64-bit system copy on 64-bit WindowsC:WindowsSysWOW64RADCUI.dllfor the 32-bit system copy on 64-bit Windows
The directory names are counterintuitive. On 64-bit Windows, System32 contains native 64-bit system files, while SysWOW64 contains 32-bit files used by 32-bit applications. Windows uses file-system redirection so that programs normally receive the architecture they require. See Microsoft’s File System Redirector documentation.
Historical file inventories show radcui.dll versions from Windows 8.1-era and Windows 10-era builds, including versions in the 6.3.9600 and 10.0.x families. The exact version and size vary by Windows build, architecture, and cumulative updates. Do not use a version list to select a DLL from an unrelated Windows installation.
Match the symptom to the likely cause
| What you see | Most likely explanation | Start with |
|---|---|---|
“radcui.dll is missing” and the path is under C:Windows |
Deleted or corrupted Windows component | Windows Update, DISM, then SFC |
| The error appeared after an update or forced shutdown | Incomplete update or component-store damage | Restart, finish updates, then DISM and SFC |
Defender Protection History names radcui.dll |
Quarantine or a detection involving the file | Check the original path and signature |
| Only one application fails | Damaged application, stale configuration, or a private DLL conflict | Repair or reinstall that application |
Error 0xc000007b or “not designed to run on Windows” |
Wrong architecture, invalid image, or damaged dependency | Repair Windows and the affected application |
| A copy exists in Downloads, Temp, or an application folder | Possible sideloading or malware | Do not run or replace it; scan and investigate |
| Several unrelated system DLLs fail | Broader Windows, disk, or filesystem corruption | DISM/SFC, storage diagnostics, and recovery |
The wording may differ by Windows release and by the executable that attempted to load the file. A message naming radcui.dll does not always prove that this DLL is the only damaged or missing dependency.
Fix radcui.dll errors in order
1. Install Windows updates and restart
A pending update may contain the correct component repair or may have left servicing incomplete.
- Open Start and select Settings.
- In Windows 11, select Windows Update. In Windows 10, select Update & Security, then Windows Update.
- Select Check for updates.
- Install all available updates.
- Restart the computer, even if Windows does not require an immediate restart.
- Open the program that produced the error again.
If the error began immediately after a particular update, open Update history. Choose Uninstall updates, select the relevant update, and follow the prompts if Windows makes that option available. Microsoft lists update removal and other recovery methods in its Windows recovery options.
Do not download radcui.dll from a search result and place it in System32. Windows servicing must restore a copy that matches the installed build and architecture.
2. Repair the Windows component store with DISM and SFC
This is the primary repair for a missing, deleted, or corrupted copy in the Windows directories.
- Open Start.
- Type
Command Prompt. - Right-click Command Prompt and choose Run as administrator.
- Select Yes if User Account Control asks for permission.
- Run this command:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- Wait for DISM to finish. It can remain at one percentage for a while.
- When it completes, run:
sfc /scannow
- Wait until the verification reaches 100 percent.
- Restart Windows and test the affected program.
DISM repairs the Windows image and component store. SFC then checks protected system files and replaces damaged copies from that repaired store. Microsoft recommends this order in its System File Checker guidance.
A successful SFC result may say that Windows Resource Protection found no integrity violations or found corrupt files and successfully repaired them. If SFC says it could not repair some files, restart and run the two commands again. If the same corruption returns, continue with the recovery steps below rather than copying a DLL manually.
If repeatedly hunting through repair commands is becoming difficult, Outbyte PC Repair can show additional Windows problems through its free scan, while repair actions are handled by the full version; it is optional, and DISM/SFC remain the appropriate built-in repair for this Windows component.
3. Check whether antivirus quarantined the file
Windows Security may have removed a file because it was modified, replaced, or detected in an unexpected location.
- Open Start and select Windows Security.
- Choose Virus & threat protection.
- Select Protection history.
- Look for an event mentioning
radcui.dll. - Expand the event and note the original file path and detection details.
Only consider restoring a file if it was the genuine copy from the Windows system directory and its Microsoft signature can be verified. Do not blindly select Allow on device. If the file was located in a temporary folder, Downloads, or an application directory, treat it as potentially unsafe.
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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesProtection History does not retain events indefinitely, so an older quarantine event may no longer appear. Microsoft explains quarantine, restoration, and detection behavior in its Protection History documentation.
After addressing a confirmed false detection, run DISM and SFC so Windows can restore a trusted copy. If malware is possible, update Defender and run a Full scan. For a more persistent threat, use Microsoft Defender Offline scan from Virus & threat protection > Scan options. Microsoft’s virus and threat protection guide describes these scan choices.
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4. Verify the file path and Microsoft signature
A same-named file is not automatically legitimate.
Open an elevated Command Prompt and run:
where radcui.dll
dir "%windir%System32radcui.dll"
dir "%windir%SysWOW64radcui.dll"
where may show more than one result. The expected Windows copies are under the two system directories described earlier. A result in an application directory, a user profile, a temporary folder, or Downloads requires investigation.
You can check the Authenticode signature in PowerShell:
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Get-AuthenticodeSignature "$env:windirSystem32radcui.dll"
Get-AuthenticodeSignature "$env:windirSysWOW64radcui.dll"
For a genuine Windows copy, the status should indicate a valid signature from Microsoft. A missing or invalid signature does not prove malware by itself, but it means you should not replace, register, or trust the file without further investigation.
If an application folder contains its own radcui.dll, do not overwrite the Windows copy with it. DLL search-order hijacking can cause an application to load a malicious or incompatible file before Windows searches the system directories.
5. Repair the application that reports the error
If Windows has valid system copies and only one program fails, the application may have a damaged installation, stale RemoteApp configuration, or an incorrectly bundled dependency.
Try the program’s built-in repair option:
- Open Settings.
- Select Apps.
- Choose Installed apps in Windows 11, or Apps & features in Windows 10.
- Select the affected application.
- Choose Advanced options, if shown.
- Select Repair.
- Test the application.
If there is no Repair option, uninstall the program, restart Windows, and reinstall it using the developer’s official installer. For a game, use the launcher’s Verify files or Verify integrity command before reinstalling.
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Do not assume that a radcui.dll error requires Visual C++ redistributables. This file is a Windows component, not a Visual C++ runtime. Install or repair a runtime only when the error separately names a file such as VCRUNTIME140.dll or MSVCP140.dll.
6. Check architecture and driver-related problems
A 32-bit application should use the 32-bit Windows component through WOW64. A 64-bit application requires the 64-bit copy. Never copy the file from SysWOW64 into System32, or the reverse.
This matters particularly for:
0xc000007b- “Bad Image”
- “not designed to run on Windows”
- errors that began after replacing application files
Run DISM and SFC, then repair the calling application. Also install pending Windows updates, because system components and drivers are serviced together.
If the problem appeared alongside broader hardware or display failures, open Device Manager:
- Right-click Start.
- Select Device Manager.
- Expand categories showing a warning icon.
- Right-click the affected device and select Update driver.
- Choose Search automatically for drivers.
- Restart if Windows installs an update.
Updating a driver will not normally replace radcui.dll, so treat this as a secondary step, not the main repair. Outbyte Driver Updater can reduce the manual work of identifying stale drivers through its free scan, while driver installation is handled by the full version; use it only as an optional aid and obtain critical drivers from the hardware manufacturer when possible.
7. Use System Restore if the failure is recent
System Restore is useful when the error began after an update, driver installation, or system change.
- Press Win + R.
- Type
rstrui.exeand press Enter. - Select Next.
- Choose a restore point dated before the problem began.
- Select Scan for affected programs if available.
- Review the changes.
- Select Next, then Finish.
System Restore normally preserves personal files, but it can roll back system files, drivers, updates, settings, and installed programs. Microsoft provides the procedure in its System Restore guide.
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8. Investigate disk or broader Windows corruption
If DISM and SFC repeatedly find corruption, or several unrelated Windows DLLs fail, back up important files and investigate the storage device.
Review:
- The drive manufacturer’s health diagnostics
- Event Viewer entries for Disk or NTFS errors
- Windows servicing errors
- Whether the computer has experienced unsafe shutdowns
Disk failure is not specific to radcui.dll, but repeated system-file corruption can indicate a broader storage or filesystem problem. Repair Windows or replace failing storage only after securing your data.
Why manual DLL downloads and regsvr32 are usually wrong
There is no official standalone Microsoft radcui.dll redistributable package. The safe sources are Windows itself, Windows Update, the Windows component store, or matching Windows installation media.
Random DLL download sites can provide:
- Malware using the familiar filename
- The wrong Windows build
- The wrong 32-bit or 64-bit architecture
- An invalid or missing Microsoft signature
- A file with incompatible dependencies
The file may also be missing because another dependency is damaged. Installing a replacement therefore often leaves the real problem untouched.
Do not normally run:
regsvr32 radcui.dll
regsvr32 applies to DLLs that provide a self-registration entry point such as DllRegisterServer. Public export information for radcui.dll does not establish that it supports this repair method. The command may instead report that DllRegisterServer was not found. DISM, SFC, Windows Update, and application repair are the correct paths.
If the error remains after these steps
Escalate in this order:
- Install all pending Windows updates.
- Run DISM and SFC again from an elevated Command Prompt.
- Review SFC details and
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- Repair or reinstall the affected application.
- Use System Restore.
- On supported Windows 11 releases, consider Settings > System > Recovery > Fix problems using Windows Update, where available.
- Use installation media or Reset this PC only after backing up data and reviewing the selected reset options.
A clean reinstall or reset is a last resort, especially when only one application is affected.
FAQ
Is radcui.dll safe?
A genuine copy in System32 or SysWOW64 with a valid Microsoft signature is normally a legitimate Windows component. A file with the same name in an application, temporary, or Downloads folder may be unrelated or malicious.
Is radcui.dll part of Windows 10 and Windows 11?
It is associated with Windows RemoteApp and Desktop Connections, and public inventories document it across older Windows releases. Exact inclusion and file details vary by edition, build, and servicing state, so do not use an old version table as proof that a particular file belongs on every Windows installation.
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Should I download radcui.dll?
No. Restore it through Windows Update, DISM, SFC, component repair, or matching installation media. Avoid arbitrary DLL download sources.
Should I register it with regsvr32?
No, not as a standard fix. The available export information does not show the normal DllRegisterServer entry point required for manual registration.
Why does the error remain when the file exists?
The loader may be reporting a damaged image, wrong architecture, invalid signature, or another missing dependency. Check the path and signature, run DISM/SFC, and repair the application that reports the error.
Is radcui.dll a Visual C++ runtime?
No. It is a Microsoft Windows RemoteApp and Desktop Connection UI component. Do not install Visual C++ packages unless the error also identifies a Visual C++ runtime file.
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