booster_mm.dll Missing: Repair the WinHL-Booster Server Plugin

booster_mm.dll is not a Windows system file. It is the Windows plugin DLL for WinHL-Booster, an old Metamod add-on used by Half-Life GoldSrc dedicated servers.

The safest fix is to restore the complete WinHL-Booster package to the server’s mod directory and correct the Metamod configuration. If the server no longer needs Booster, remove its stale entry from plugins.ini instead of downloading a loose DLL.

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What booster_mm.dll belongs to

The file is commonly identified as WinHL-Booster Metamod Plugin DLL, associated with developer Jussi Kivilinna. It is loaded by Metamod on a dedicated Half-Life, Counter-Strike, or another GoldSrc server.

It is normally found below the server’s game or mod directory:

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<Half-Life server><mod>addonsboosterbooster_mm.dll

For a Counter-Strike server, the path may look like:

C:Servershldscstrikeaddonsboosterbooster_mm.dll

The exact drive and folder depend on where the server was installed. The important part is that the DLL belongs inside the mod directory, not inside Windows.

Historical file catalogs commonly identify this as an old 32-bit Windows DLL. That means a 64-bit edition of Windows may run the surrounding 32-bit GoldSrc server, but the plugin must match the server process and platform.

What the error messages mean

You may see messages such as:

• booster_mm.dll was not found
• The program can't start because booster_mm.dll is missing
• Failed to load booster_mm.dll
• Error loading booster_mm.dll
• The specified module could not be found
• booster_mm.dll is either not designed to run on Windows or it contains an error

These messages do not all mean the same thing.

A missing-file message usually means the file was never extracted, was deleted, or is in a different folder from the one configured in Metamod. “The specified module could not be found” can also mean that a dependency used by the plugin is missing.

The “not designed to run on Windows” wording can indicate a damaged file, an incorrect architecture, a Linux .so file renamed as a DLL, or an incompatible binary. The message alone does not prove that Windows itself is damaged.

Fix 1: Restore the complete WinHL-Booster package

Time needed: 10 to 20 minutes

This is the most likely fix when the server previously worked and the error appeared after moving, re-extracting, or cleaning the server folder.

Do not start by downloading booster_mm.dll from a random DLL website. The DLL may be modified, incomplete, the wrong architecture, or missing companion files. A loose replacement also does not correct a wrong Metamod path.

Step 1: Stop the server

Close the dedicated server cleanly. If it runs as a service or through a control panel, stop it there first.

Do not replace plugin files while the server is running.

Step 2: Find the active game directory

Locate the folder containing the server’s executable and the mod folder. Common examples include:

C:Servershlds
D:GameServersHalf-Life
C:srcds

Then open the relevant mod directory, such as:

cstrike
valve
dod

The expected plugin location is:

<mod directory>addonsboosterbooster_mm.dll

Check the filename carefully. It must be booster_mm.dll, not booster_mm.dll.dll, booster_mm (1).dll, or a file with a hidden extension.

In File Explorer, select View → Show → File name extensions so Windows displays the real extension.

Step 3: Restore the original package

Use the original WinHL-Booster archive supplied with the server or obtained from the server’s known administrator or historical software source. Extract the complete directory structure, not just one DLL.

After extraction, confirm that this file exists:

<mod directory>addonsboosterbooster_mm.dll

If the package includes configuration files or other Booster files, preserve their original folder structure.

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There is no currently maintained official WinHL-Booster download page established for this old plugin. Treat third-party archives as unverified unless you can confirm their provenance and compare the file with a known-good copy.

Step 4: Start the server and check the console

Start the server and watch the console or log. A successful repair should remove the missing-file message and show that Metamod loaded the plugin.

If the same error remains, the server may be using a different mod directory or a different plugins.ini file. Continue with the next fix rather than copying the DLL into Windows folders.

Fix 2: Correct the Metamod plugins.ini entry

Time needed: 5 to 10 minutes

Metamod normally reads:

<game directory>addonsmetamodplugins.ini

Plugin paths are relative to the game directory, not relative to the metamod folder.

Open the active plugins.ini in Notepad and check for an entry like this:

win32 addons/booster/booster_mm.dll

The parts mean:

• win32 tells Metamod to load a Windows DLL.
• addons/booster/booster_mm.dll is the path relative to the mod directory.
• Forward slashes are valid and avoid confusion in Metamod configuration files.

For example, if the active mod directory is:

C:Servershldscstrike

then this entry points to:

C:Servershldscstrikeaddonsboosterbooster_mm.dll

Check the following:

1. The plugins.ini file is inside the active mod directory.
2. The server is launching that same mod directory.
3. The line spells booster_mm.dll exactly.
4. The booster folder is directly inside addons.
5. There are no duplicate Booster lines.
6. The line is not commented out with a semicolon if you intend to load it.
7. The entry does not point to a different mod, backup folder, or old server installation.

If the server no longer needs WinHL-Booster, comment out the line:

;win32 addons/booster/booster_mm.dll

Start the server again. If it now starts normally, Booster was the obsolete component preventing a clean launch.

Fix 3: Remove Booster instead of repairing it

Time needed: 5 minutes

WinHL-Booster is an old server plugin. If the server operates correctly without it, removal is usually safer than forcing an obsolete binary to load.

1. Stop the dedicated server.
2. Back up addonsmetamodplugins.ini.
3. Remove or comment out this line:

text
win32 addons/booster/booster_mm.dll

1. Start the server.
2. Confirm that the server reaches its normal running state.
3. Only after testing, delete the addonsbooster folder if it is no longer needed.

Do not delete the folder first and leave the active Metamod entry behind. That guarantees another missing-plugin error at the next start.

If the server crashes only when Booster loads, remove the entry temporarily even if the DLL is present. A successful file lookup does not prove that the plugin is compatible with the current Metamod build or server environment.

Fix 4: Check Windows Security quarantine

Time needed: 5 to 15 minutes

Old unsigned server plugins can attract antivirus detections, particularly when extracted from unofficial archives. A quarantine event is not automatically proof of a false positive or proof that the file is malicious.

1. Open Start.
2. Search for Windows Security.
3. Open Virus & threat protection.
4. Select Protection history.
5. Look for an event involving booster_mm.dll or the Booster archive.
6. Expand the event and inspect the detection name and original path.
7. Compare that path with the server’s actual addonsbooster directory.

Only restore or allow the file after verifying the archive’s source and integrity. If the detection is unclear, leave the file quarantined and use a known-good server backup instead.

After restoring a validated file, add an exclusion only for the dedicated server directory if your security policy permits it. Do not broadly disable antivirus protection for the whole system.

Fix 5: Check the Windows/Linux and 32-bit mismatch

Time needed: 5 to 15 minutes

booster_mm.dll is a Windows plugin. It cannot be loaded by a Linux GoldSrc server.

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A Linux server normally requires a Linux shared-object plugin, using a .so file and a Linux-specific Metamod entry. Renaming a Linux .so file to .dll does not convert it. Likewise, renaming this DLL to .so will not make it work on Linux.

Check the server host:

• On Windows, use the 32-bit Windows Booster build if you are restoring it.
• On Linux, obtain the matching Linux build from the original distribution if one exists, or remove Booster.
• Do not mix files from Windows and Linux server packages.

A 64-bit Windows installation can run many 32-bit applications, but the plugin must match the GoldSrc server process. A damaged or non-Windows file can produce the “not designed to run on Windows” error.

If you need to identify the file architecture, inspect the PE file with a reputable dependency or binary inspection utility. Do not rely on a download page claiming that the DLL is x64 when the available file records identify the historical plugin as 32-bit.

Fix 6: Investigate a missing dependency

Time needed: 15 to 30 minutes

A loader message can name booster_mm.dll even when a library required by Booster is the actual missing file.

Use a PE dependency inspection tool on the restored DLL and look for a dependency marked missing. You can also inspect the dedicated server’s full console log for a more specific loader message.

The historical file metadata associated with this plugin lists ordinary Windows libraries such as KERNEL32.dll, WINMM.dll, and msvcrt.dll. That does not establish that installing a modern Visual C++ package is the normal repair.

If diagnostics specifically identify a Microsoft Visual C++ runtime, install the matching package from Microsoft’s official Visual C++ Redistributable documentation. A 32-bit server or plugin requires the x86 redistributable, even when Windows itself is 64-bit.

Do not install every Visual C++ release, DirectX package, or .NET runtime as a guess. Install only the dependency named by the diagnostic, then restart the server and test again.

Fix 7: Repair Windows components only when Windows has broader damage

Time needed: 15 to 30 minutes

System File Checker and DISM repair protected Windows components. They do not normally restore a third-party Metamod plugin or rebuild the addonsbooster directory.

Use them when other Windows applications are also reporting damaged system files.

1. Open Start.
2. Search for Command Prompt.
3. Right-click it and select Run as administrator.
4. Run:

text
DISM.exe /Online /Cleanup-Image /RestoreHealth

1. Wait for it to finish.
2. Then run:

text
sfc /scannow

1. Restart Windows.
2. Test the server again.

Success means DISM completes without an unrepaired error and SFC reports that it repaired files or found no integrity violations. If these commands complete successfully but the Booster error remains, return to the server path and Metamod configuration. Windows repair was not the relevant fix.

Manually hunting through system logs and repeating SFC or DISM without knowing what changed can consume time without restoring a third-party plugin. Outbyte PC Repair can scan for broader Windows problems and show what its free scan identifies, while repairs require the full version; reinstalling WinHL-Booster or removing its Metamod entry remains the definitive fix for this specific file.

Fix 8: Check recent driver or system changes

Time needed: 10 to 20 minutes

A graphics or chipset driver is not normally responsible for locating a Metamod plugin. However, if the error appeared immediately after a system migration, security change, or driver update, check whether the server host itself changed.

To inspect drivers:

1. Right-click Start.
2. Select Device Manager.
3. Expand Display adapters, Network adapters, and System devices.
4. Right-click a device.
5. Select Properties.
6. Open the Driver tab.
7. Check the driver provider, date, and version.
8. Use Update Driver only when Windows or the hardware vendor provides a suitable package.
9. If the problem began directly after an update, use Roll Back Driver when that button is available.

Do not expect a driver update to repair a missing addonsboosterbooster_mm.dll. Outbyte Driver Updater can scan for outdated drivers and show what needs attention, while driver installation requires the full version; for this error, correcting the server package and Metamod path remains the primary repair.

Why System32 and SysWOW64 are wrong

Do not copy booster_mm.dll to either of these folders:

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C:WindowsSystem32
C:WindowsSysWOW64

Those directories are for Windows and application components that use the system DLL search path. Metamod expects this plugin relative to the GoldSrc game directory.

Putting the file in a system folder can:

• Leave the Metamod path broken
• Create confusion when multiple copies exist
• Expose Windows to an untrusted binary
• Cause the wrong copy to be loaded by another program
• Make later cleanup more difficult

The correct location is the server’s mod directory under addonsbooster.

Why regsvr32 does not apply

Do not run:

regsvr32 booster_mm.dll

A .dll extension does not mean that a file should be registered. regsvr32 is intended for DLLs that expose Windows registration routines, commonly COM or ActiveX components.

Metamod loads Booster as a plugin and expects Metamod-specific entry points. Registration does not install the plugin, correct plugins.ini, or make a Linux binary compatible with Windows.

Causes of booster_mm.dll errors

Safe removal procedure

If you decide not to use WinHL-Booster:

1. Stop the server.
2. Back up the entire server directory or at least plugins.ini.
3. Remove or comment out the Booster line.
4. Start the server and verify normal operation.
5. Delete addonsbooster only after confirming it is unused.
6. Remove old backup copies that could be mistaken for the active server.

This leaves Metamod installed while removing only the obsolete plugin.

Frequently asked questions

Is booster_mm.dll part of Windows?

No. It is a third-party WinHL-Booster plugin for Metamod and GoldSrc dedicated servers.

Is it a normal client-side game DLL?

Usually not. The evidence points to a server-side Metamod plugin. A regular Half-Life or Counter-Strike client generally should not need this file in its Windows system directories.

Can I download just booster_mm.dll?

That is risky. There is no verified maintained official vendor download page for the old plugin. Use a known-good complete package or remove the stale Metamod entry. Avoid random DLL download sites.

Should I install DirectX, .NET, or Visual C++?

Not as a first step. Those packages are not established as the normal fix for this plugin. Install a Microsoft runtime only if a dependency diagnostic specifically identifies it.

Can a 64-bit Windows PC run this plugin?

It may run the surrounding 32-bit GoldSrc server under 64-bit Windows, but the plugin itself must be a compatible 32-bit Windows DLL.

What if the server runs Linux?

A Windows .dll cannot load on Linux. Use the matching Linux plugin build if the original distribution provides one, or remove Booster from the configuration.

What if the plugin loads but the server crashes?

Stop the server and comment out the Booster line. If the crash disappears, leave the plugin disabled unless you can test a known-compatible package in an isolated server installation.

Do I need System Restore?

Usually no. System Restore is a fallback for a recent system-wide change, not the normal repair for one missing server plugin. Restore the package, correct Metamod, or remove the obsolete entry first.

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