I am a forensics professional and I teach forensics in a university. Don't mess with it. If you think there is evidence of illegal activity on the computer then you need to hand it over to someone who knows proper procedure for maintaining the chain of custody, chain of evidence, etc. Anything you do may be considered tampering with evidence and could actually get the perp off on a technicality. You certainly don't want that to happen. Seriously. I could teach you how to do it, but I STRONGLY advise against doing it yourself because you could sabotage the case against the perp.