Upgrade Hell Need some Advice

Ok, i'm a bit frustrated after a long weekend putting computers together. I'm not a novice but certainly am not an expert and could use some of the expert opinions out here.

1. Made a computer awhile back for a friend. It was on the cheap side with a Pentium II based motherboard off of ebay and an old 266 processor i used to have. Has a 256 SDRAM chip, 40 gig hard drive, Win98 system, everything seems fine to me. Installed windows, peripheral cards, etc. The thing works, or seems to. Turns out after awhile the thing reboots randomly. Playing around with it, found that it would reboot at completely random times, plus as a side note it would actually seem to reboot after awhile if you even nudged the case a little. So at that time i'm thinking that the crappy motherboard and/or processor are the problem. After working on some other boards I have some extra components to put in this built one:
Pentium II 700 - confirmed working before
Abit BX6 Rev. 2.0 Board - confirmed working before with CPU
256k generic SDRAM - confirmed before with CPU/MBoard

So after installing all these newer components, I can't even get the thing to boot to windows. Took out all peripherals except the vid card. Upon startup it will cycle through the memory test, it will detect both the 40g hard drive and the CDRom drive, but instantly hangs up after the CDRom recognition, no other messages, nada nothing. I've tried everything I can think of including:
rechecking all the cables, power, ide connections
tried the old Pentium II
tried every BIOS setting i can think of
reset the CMOS in the bios

All the components are the same except the 3 listed above that were on the previous build. Was thinking power supply at one time but it does recognize the 2 IDE items.

Can't get it to go anywhere past the Hard Drive/CD Rom detection. I know this is a vague question, but anyone have an idea based upon when it's locking up as to where the problem is? Any advice at all would be well received.

Fixed by completely removing and rebuilding, probably shorted underneath would be my guess but thx for the tips.