What steps would you take to make a windows xp machine appear that it hasn't been logged on to since some past date. Not to a forensic level here, just to a casual inspection.

Fyi this is not intended to do anything destructive to someone elses machine. This is for my own use believe it or not.

And no, I'm not trying to hide from daddy that I used his computer. If you want to be sarcastic here, please come up with something half way amusing, thanks.