By the way, could bad cables attached to more simple things like the CD/DVD drives and floppy drives cause problems? Maybe all my cables were bad...

Yes, that is a possibility worth considering.

Also, I have seen stuff like this happen when running certain AGP graphics cards at 4x speed on a motherboard that doesn't properly support 4x (despite the fact that it says it does). I have sometimes had to throttle the card back to 2x to get the lockups to stop.

I have also seen bad USB-port drivers or IDE controller drivers do this sort of thing. Have you made sure to get the proper USB/IDE drivers for your motherboard from Soyo?

I would start by unplugging everything except the video card and one hard disk. See if it all works. If it does, start plugging other things in until it fails again.