Everything keeps freezing sporadically

[Noodle Boy]

My computer is acting really wierd (again). Every few seconds while im surfing the net or opening a file or other activities (no pron lol) my computer would just freeze and i can't do a thing, and then everything goes back to normal, then the same thing happens all over again. This didn't happen yesterday, so I don't know what can be the problem. I ran Mc Afee Virus Scanner, no viruses, I ran Ad Aware and Spybot: Search and Destroy and no spy or adware...so what can be the problem? Perhaps it's a bug with service pack 2 or maybe it could be firefox, maybe both, maybe neither, but I really need help with this because I REALLY don't feel like reformatting my drive.