XP Pro logs off immediately after you log in

HERE IS THE FIX

1. Navigate to
"HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWinlogon"
2. If there is a key named "OldUserinit", delete the "Userinit" key and rename the "OldUserinit" key to "Userinit".

3. The "Userinit" key should now say
"WINDOWS_PATHsystem32userinit.exe,"

"WINDOWS_PATH" is relative to where you have your windows installed.
Mine would be "C:WINDOWSsystem32userinit.exe,"

Now you can log in again

Who changed my Userinit key?

Spyware. The program is called "Search Assistant" and is located at "Program FilesWindowsSA". It also has some "omni*.*" files in "WINDOWSsystem32" dir that are linked to "Userinit" key. If you remove this spyware (using Ad-aware, etc.) the "omni*.*" files are deleted and you can't log in.
How to edit registry when I can't log in?

- Use recovery console - read the manual or browse the web on how to edit registry in recovery console.
OR

- Use another machine on your network: Open regedit and select "File->Connect Remote Registry..." and in the dialog box select computer that has log in problems to view its registry.


finally
Rename the userinit.exe to wsaupdater.exe

Additional instructions
Fix Windows XP Log On/Log Off Loop