How to register or unregister a DLL?

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