Another bit missing: what OS are you running?
Our eMachines running XP had similar problems to what you're describing. Same thing, in fact. Then, after a few weeks, it started taking around twenty minutes (no kidding) to boot up all the way into windows, and was always busy whether we were doing anything or not . . . and we had Norton AntiVirus with current definitions running the whole time, and LavaSoft's Ad-Aware Personal, and Spybot Search & Destroy. It can happen. We had to reformat the thing to fix it, because we took it in to a shop for a virus-cleaning and it did no good whatsoever, and we couldn't get it to run anything at all. After reformatting, it was fine.