It can also be caused by a corrupt User Profile. Try logging on as the Administrator and if that works OK create another User account.
Enter the Recovery Console
Boot the system using the Windows XP CD-ROM. In the first screen when the Setup begins, read the instructions press "R" (in the first screen) enter the Recovery Console.
1: C:\WINDOWS
Which Windows Installation would you like to log on to
(To cancel, press ENTER)?
After you enter the number for the appropriate Windows installation, Windows will then prompt you to enter the Administrator account password.
Note If you use an incorrect password three times, the Windows Recovery Console closes. Also, if the Security Accounts Manager (SAM) database is missing or damaged, you cannot use the Windows Recovery Console because you cannot have correct authentication. After you enter your password and the Windows Recovery Console starts, type exit to restart the computer.
Type the following command and press Enter.
CD SYSTEM32
(If that does not work, try CHDIR SYSTEM32)
At the prompt type in
COPY USERINIT.EXE WSAUPDATER.EXE
Quit Recovery Console by typing EXIT and restart Windows.
You'll be able to login successfully as you've created the wsaupdater.exe file (now, a copy of userinit.exe)
"WARNING MODIFYING REGISTRY INFORMATION IS DANGEROUS"
Backup the Key before making changes.
Now, change the USERINIT value in the registry
Click Start, Run and type Regedt32 and press Enter.
Navigate to:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon
In the right pane you will see that the value of the Userinit key is incorrectly set to "wsaupdater.exe,"
In the right-pane, change the value of Userinit to C:\WINDOWS\system32\userinit.exe,
Type the above value exactly as given, including the comma. Also, change the path to userinit.exe appropriately if Windows is installed in a different drive.
Close Registry Editor and restart Windows
Keep us informed as to your progress if you require further assistance.
