Ok, stop.
I am rather sure, that if something is wrong with the BIOS, you wouldn't have a computer.
And if something is wrong with a hard drive, you would know it in all kinds of error-ry, data-lossy and possibly, noisy ways.
And generally, hardware issues do not get temporarily fixed by formatting, because, being hardware issues, they couldn't care less what software does. If the disk was bad, it would be bad continuously.
What this sounds like, is either a virus, which every time you re-install for some reason. Or some kind of conflict of something with something, including potentially Norton.
One thing worth doing, is to alt-ctrl-del when the computer is slow, and check the process thingy to see what thing (if any) uses the most CPU.