Windows Log on and Log off immediately

* See the below article
http://support.microsoft.com/kb/555648

Fix:1. Boot using your winxp cd.2. Enter recovery console.3. at the command prompt go to
C:/windows/system32
4. next type:
copy userinit.exe wsaupdater.exe
5. exit and reboot normally. You should now be able to logon. But you're not done yet!
6. run regedit
7. find the Userinit key in:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\
8. modify the entry:
C:\WINDOWS\System32\wsaupdater.exe
so that it reads:
C:\WINDOWS\System32\userinit.exe
That should do the trick! no reinstalling windows required!

or
copy c:\windows\system32\userinit.exe c:\windows\system32\wsaupdater.exe
expand d:\i386\userinit.ex_ c:\windows\system32
step1: expand d:\i386\userinit.ex_ C:\
step2: copy c:\userinit.exe c:\windows\system32