I worked in the same general area with a guy who tried to bully me. He was a domain admin, and would break into my PC and delete stuff, he verbally tried to humiliate me in front of my co-workers, made references to me being a female, and though I can't prove it, I'm sure he's the one that sent the email under my account to the whole dept announcing my resignation. He was also the Exchange admin, and I never left my PC unlocked. Anyway, I finally reminded him one day in front of about 30 co-workers that I new him when we were kids, and that my Dad had worked with his, and that I remembered what happened when he was a kid, and unless he wanted the whole department to know all about it, he'd sit down, shut up, and leave me alone. It all stopped. He tried something similar to two others, but they were both really good about giving him some creative verbal slap downs. I complained about his harrassment of my female status, and someone else complained based on his religious harrassment, but HR and administration wouldn't do anything about it.

I no longer work there, I make more than him, and I'm quite happy. Revenge is sweet.