Computer locks up

2 days ago, I was using my computer and it seemed fine aside from not loading webpages. I didn't think of anything at the time - it just seemed like it was acting up and needed a stern reboot. Yesterday, I turned it on and, everything loaded fine but when windows started, things go INCREDIBLY slow. I would click the start menu and after 10 or so seconds it would pop up and disappear. I tried pressing ctrl-alt-del and it would take 20 seconds for it to come up. I'd click on an icon and it would disappear for awhile and reappear later. I have no idea what the problem is, although my inkling is that it maybe some type of hardware failure - memory perhaps? But then again, why would the computer start ok if memory is a problem. I haven't run any spyware removal programs in a while although I haven't been using my computer all that much anyways. Is there anyway for me to fix this without having to reformat the whole darn thing again?