Hello.
Here is a solution that WILL (or should) work IF you follow the steps carefully.
I am not responsible for any damages caused..
(you need administrative rights for these)
1. Get a hold of another computer (with the same Service Pack, same language, etc. as your own computer), with the default XP login screen.
2. Get a copy of the C:\windows\system32\logonui.exe file from the other computer and get it on your desktop (via USB stick, cd, internet, etc.)
3. Change the name of logonui.exe (on your desktop) to logonuidefault.exe
5. Copy the logonuidefault.exe from your desktop and paste it into C:\windows\system32\
6. Now open the start menu and select Run..
7. Type in regedit and press OK.
8. In regedit, open the menu (on the left) like this:
Expand HKEY_LOCAL_MACHINE –> SOFTWARE –> Microsoft –> Windows NT –> CurrentVersion –> Winlogon (click on Winlogon)
Now, in the right panel, change the UIHost value from logonui.exe TO logonuidefault.exe
Reboot, and you should have the original screen back.