Correct, there are lots of low level drivers that basically will be different, its trying to talk german to a frenchman
As for teh PC, try resetting teh CMOS by removing the battery off teh m/board for a good 30 mins then try booting with just CPU, GFX and 1 stick of ram. Remove everything else. If this works, try adding stuff back one piece at a time. If you don't get anywhere, try a different stick of ram and gfx card
If you still don't get anywhere, buy one of those PCs you were selling