Are you having a problem when you try and logon to Windows XP it then logs out straight away? If so then you may have a corrupted or infected userinit.exe file.

We come across this problem more often when the customers antivirus programs detects an infection and then deletes userinit.exe file or the infection changes the registery and deletes the same file. The customer will not know the problems exists until they reboot the machine. 

Warning:

Before you attempt this fix we recommend backing up all user data, just in case. You will also need some technical knowledge in using the following, Windows start up disk, Windows Recovery Console and the Windows Registry Editor. 

Ready?   

First boot using your Windows XP start up disk.
Then select R to enter the recovery console.
At the prompt type cd c:/windows/system32
Now type x:\i386 D x being the drive letter of your cd-rom drive
Then type: copy userinit.ex_ wsaupdater.exe
Then type: copy userinit.ex_ userinit.exe
If both files sucessfully copies across then type Exit and then let the machine reboot normally.

You should now be able to logon normally. 

Now you are not done just yet!

Click on the start button then select Run, in the open field type in regedit
Now look for the Userinit key in: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon\
Modify the entry: C:\WINDOWS\System32\wsaupdater.exe so that it reads: C:\WINDOWS\System32\userinit.exe
Now close the registry editor.

That should be it, now restart you machine to make sure it logon properly. 

We hope this solution works for you!