You have got to be kidding!
First, where is legal counsel for the company?
Next, why doesn;t the wife simply pick up the computer and take it out of the house? Is the guy there 24/7?
Does she have access to the computer? If so, can she get it online so you can affect changes via the internet? Piece of cake to do.
The fact he is a shareholder , unless he is somehow contractually allowed the possession of the computer, does not entitle the guy to company property.
If all else fails, go to the hardware store and buy a 3 pound sledge hammer. Let the wife take it home and kill the computer.
I would presume preventing the use and access to company files is the ultimate goal, correct? Let the guy deal with the damage, if he feels it was incorrect, after you stop his actions.
and if the gal is the scared of the guy, she needs to file the appropriate paperwork in court to have him removed from the home or find other accomodations. If she fails to act on this, I would suspect she is pulling your leg. You do not stay in a situation where you are afraid. It is one of the most basic instincts and levels of human behavior to seek safety.

