Originally Posted by
C0FFINCASE
Agreed. The HDD space doesn't really have anything to do with the speed of the computer unless you're talking about having it filled to capacity. The processor and ram are responsible for that. Unless you're dealing with something that requires a video card, in which case you have to account for that as well.
If it was fast and has slowed down maybe run CCleaner and fragment your drive(I'd suggest defraggler). Clean up your registry as well. Make sure a ton of crap doesn't load at startup. Typical things, you already know you should do but most likely aren't. After that you could lower visual settings in favor of performance.