keyboard and mouse not working in xp

I am working on a Dell XPS400. When the XP login screen comes up, the keyboard and mouse will not work. They do work with a bootable disk (UBCD).
I have restored the registry to a time when it was working. No luck. Same thing. I have tried safe mode, command prompt and every other option in the boot menu with the same result. Have also tried XP repair. It gets to the part where user input is needed for computer name and no keyboard or mouse. I have run out of ideas. Anybody have any? Thanks

 

Have you checked your drivers ??

 

Read post #22

Code:

http://forums.anandtech.com/showthread.php?t=2041146

apparently the computer kills the USB ports after it POSTS.
It sounds complicated but no other solution seems to work.

 

Hi my friend , if previous solutions didn't work you can remove your cmos battery for two minute or so after put it back restarting your system :wave

http://www.youtube.com/watch?v=ao866I9XpTo

 

I have removed the CMOS battery. Same result. Also tried the suggestion from plodr. Again, didn't work. As for the drivers, when I attempted a Windows repair, it would have put them in before before I got to the computer name screen. Thanks for the help, but I am stumped. Any other ideas?