My computer won't start in windows xp PRO

i did a bit of deleting and updating and I changed the way my computer
was going to start (changed users ) I also changed to blue welcome screen now when I turn computer on everything works perfectly until windows starts to boot and then my mouse and board turn off.Tried everything on F8 all works but cannot get on once windows starts booting because I loose mouse and board connection. I installed another Windows XP pro program on the same hard drive works perfectly when I try to boot from my original program same problem.
When I tried to access safe mode (all modes in F8) in my original problem it displays a message debug is turned on.
Please can anyone give some suggestions I will try removing the battery and removing everything from the computer turning it off and seeing if that works
I ran an AVG rescue disc no viruses present.