Thanks for responding again Madmonkey. I went through and unplugged/replugged everything, and found that it still wouldn't turn on.

I then grabbed a really cheap 400W PSU out of a spare computer (the thing weighs literally nothing...I was kind of scared to use it). Anyway, I hooked it up, and the computer booted up like a charm...

I'm not expert, but I'm guessing that the PSU had something to do with it. I'm going to go buy a new PSU for the computer later on, and hopefully my problems with that computer stay away.

Thanks again for your help

FYI, it was the PSU that was bad. Replaced it with a new one and it works like a charm...so far

Nice work Bravo. Marked as Resolved (for now).