Don't Touch That Computer!!
Michael Fitzgibbon has a post in his Thought's From a Management Lawyer blog that refers to an article about computer forensics. The article points out that if there is a suspicion that an employee has used his/her computer improperly, or it may contain evidence of wrongdoing, it is crucial to have a forensics expert look at it. Resist the temptation to look at it yourself, or even have your IT department do it. Indeed, don't even turn it on or off.
The article states that: Such amateur searches are as damaging to the integrity of the computer forensics investigation as having a company's security guard muck around at a crime scene prior to the arrival of the criminal forensics experts
And of course it is much better if the business has a computer and internet use policy in place.