My roommate gave me his old computer that no longer worked due to a ton of viruses from a lot of random downloads. I took it in to a computer repair shop and they installed a new hard drive and said it should be working fine, now. It is definitely working and seems to be working well for the most part, but it's really slow. I have a ton of free disk space, so it shouldn't be that. I was just wondering, is it possible there's still viruses or anything that's keeping the computer running so slow?