REGSVR32

Register or unregister a DLL.

Syntax
      REGSVR32 [/U] [/S] [/C] [/I:[ Command_Line ]] DLL_Name

      REGSVR32 [/U] [/S] [/C] /N /I:[ Command_Line ] DLL_Name

Key
   
   /u          Unregister Server.
   /s          Silent - no dialogue boxes.
   /c          Console output.
   /n          Don't call DllRegisterServer
   /i          Call DllInstall (or DllUninstall if /u is specified)
   Command_Line  An optional command line for DllInstall

Examples

Unregister (disable) XP Zip folders
REGSVR32 /u C:\Windows\System32\zipfldr.dll

Unregister (Disable) CAB file viewer:
REGSVR32 /u C:\Windows\System32\cabview.dll

Register (enable) XP Zip folders
REGSVR32 zipfldr.dll

Register (enable) CAB file viewer:
REGSVR32 cabview.dll

Register Windows Update DLLs (for those times when XP repair breaks Windows Update)
regsvr32 /s wuapi.dll
regsvr32 /s wuaueng1.dll
regsvr32 /s wuaueng.dll
regsvr32 /s wucltui.dll
regsvr32 /s wups2.dll
regsvr32 /s wups.dll
regsvr32 /s wuweb.dll

Register DAO 3.6 (Data Access Objects):

REGSVR32 "C:\Program Files\Common Files\Microsoft Shared\DAO\DAO360.DLL"

It costs nothing to register and will only take a moment...

Related:

Delsrv - unregister a service with the Services Control Manager. (Win 2K ResKit)
MSIEXEC - Microsoft Windows Installer
RUNDLL32 - Run a DLL command
Q249873 -Regsvr32 usage and error messages