Just a quick thing. Was the virus "Antivirus 2009" that poped up on your screen telling you that you had a very bad virus. And did you click on it to remove said viruses.
Because "Antivirus 2009/2010" Is a virus that looks like windows defender and when It installs you have to remove it manually to get rid of it. And if you Bought the virus (It takes you to a place where you can buy the supposed removal tool) IT can cause even more problem.
Did this happen to you?
If not what Antivirus program did you use.
And Also, Grab a distro of Linux off the web and Load it on to a CD. Put that in your drive and that would tell you if the drive itself is bad.
And that virus I just mentioned I had a run in with it awhile back. Flashed the bios/cmos and reinstalled and still it came back after awhile.
So Installed linux on the computer and haven't had any trouble.