Glad you got it going :D
I dunno why I didn't mention, I guess I was hadn't payed much attention but if anyone else gets this problem check, double check and triple check your RAM, IDE cables and expansion cards are properly seated, you never know what can happen if they're not, I've seen computers behave oddly because of seemingly fine kit installed correctly but it's turned out that maybe the contacts weren't completely connecting or whatever...
Reinstalling your CPU is probably further than you need to go usually but again, glad it seemed helped in this case :)
Talking of cases, I've seem computers not boot correctly when installed in certain cases too so if all else fails try the computer without it's case :)