Hi Ryanmt....
Seeing that you are having problems with two different OS's, I'd say your probably right that it is a hardware related problem.
Probably one of three things, either the BIOS, the mobo or the powersupply, I'd say the latter most likely. I doubt if its a memory problem, because you said that once the OS does load, it is stable.
You mentioned that you had a 300W PS, but didn't mention the brand name. Many POST related problems can be attributed to a faulty or low quality (inadequate) PS.
Also, I'd check to make sure that all cables/connectors are secure, and that all cards are secure in the slots.
Check Abits site for any BIOS updates.
Finally, do you receive any "beep" error codes when you start up? If you do, make note of it to check its meaning. Your Abit mobo has an Award BIOS, so it should be fairly easy to track down the meaning of any error codes.