I want to bring back an old computer that belongs to my wife. It is infected with what I cannot imagine. It will not boot up. What I am thinking is to open it up , remove the hard drive and either replace the hard drive and do a fresh install of an OS or formatting the infected hard drive and reinstalling on that drive. My question is would it be advisable to replace the hard drive or will formatting the original hard drive be acceptable? Both computers are Acers if that matters. Thanks to all for any input.