A system that is more than a few years old may be having an underlying problem with its hard drive. When you rebuilt the O/S you may have only done a quick format of the hard drive which wouldn't catch serious problems with the drive. A great program to test the hard drive is SprinRite by Steve Gibson over at http://www.grc.com. When I get a new drive I run SpinRite and try to run it once or twice a year on my drives to help solve these type of problems.
Smosh tells CNET what it took to make it big online
Internet sensations Ian Hecox and Anthony Padilla discuss how YouTube has changed and why among all their goals, "real TV" isn't an ambition.