you wouldn't normally think of the cpu as faulty ....
but I have seen it happen.

also, have you re-burnt your knoppix CD
it may be faulty too

I had a 2nd hand system that booted 'fine' after i changed the mobo
updated the hardware in registry fine ....
but then, later, it wouldn't find the hdd
took an age before i realised the PSU must have been subtly faulty
as the mobo powered on ok
and the cd-roms were found ok
but not the hdd

knoppix in debug mode
would probably be the same as windows in safe mode
you can get it to work as long as you don't use a part of the system that requires the use of the part of your cpu that is faulty