Spontaneous crash, doesn't find CD, asks for A: and crashes

It could be the IDE controller - did you try the secondary IDE?  It could also be the hard drive, and you need to try a different one.  If these don't pan out, the last thing I would check is the power supply, in case it's failing.  Swap a new one in, or one from another machine that's compatible.

Did you try running with the basics not mounted in the case?  It's possible it's shorting out on the case.

I've tried a bunch of different configurations in 2 different machines. For clarity, my second machine has a Soyo Dragon SY-K7V Motherboard, and it's this one that I am typing on at the moment (big improvement!). Both machines definitely have problems with the IDE controller. The SOYO machine has 4 IDE slots: the first one seems to be problematic with the HD's, but works with one of my CD drives. I tried plugging in to 3 and 4 with no results at all. I looked up jumper settings in the manual and found 1-2 supports RAID 0 or 1, and 2-3 supports Ultra 33/66/100. I'm not sure what RAID is, but Ultra 33/66/100 sounds like HD support to me. So, I made sure 2-3 was the setting, and still neither IDE 3 or 4 work for the HD's or CD drive. So, right now, I have a working configuration with IDE 1 connected to one CD drive, and IDE 2 connected to 2 HD's. How do I get IDE 3 and 4 to start working? And, why does IDE slot 1 not support my HD's anymore?

Now back to machine #1. I disconnected IDE cable 1 and connected it to IDE slot 2 (machine #1 only has 2 slots). I was able to get the machine to boot all the way into Windows. Once in Windows, the system spontaneously powered down after approximately 15 seconds. This machine use to do this when the cable was connected to IDE slot 1 as well. It quickly degraded to spontaneously powering down while powering up. Does this indicate that the motherboard is fried on machine #1?