I bought my computer from a friend of a friend about 3 months ago. It’s a Toshiba with Windows Vista. I felt that it wasn’t running quickly enough so I did a quick scan which turned up lots of hits for not so legal cites (porn, illegal downloads, etc) how do I clean my computer so that it runs at full speed and doesn’t give my the "you have a security problem" message? is there any way to do it for free?