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

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

how to install dll file in xp using dos:

Register DAO 3.6 (Data Access Objects):

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