You would have to have screen sharing enabled or telnet enabled.
If you can get onto the machine, you could get into terminal and delete files in the file system. You might be able to use a terminal command to reformat the hd.
This might not be legal. I have no idea. The more I think of it, I suspect it would be marginal at best. It probably would not be legal. he would claim ownership right via a free rental. Not worth it.
I'd consider calling the police.
Or sending a registered letter and wait awhile. send a second registered letter & state you will call the police on a stated date. Call police.
Thank you both, BDAqua and rccharles, for chiming in with your best ideas for dealing with an impossible problem.
The situation has turned out to be more sordid than I imagined, but I do have my PowerBook back.
If you have any insights about how I can figure out whether any damage has been done to my computer or whether any of my data has been shopped, I love to hear them.
In any case, thanks again.
Not knowing your age, I will assume for now you are of age to be concerned about credit.
If you had *any* financial data on the drive, pull a credit report immmediately and look for anything you did not authorize. Also you can "freeze" your credit profile with Equifax/Experian/TransUnion for $5 per agency so that even you cannot add entries without un-freeze.
Others may call me paranoid for advising, but this may end up being necessary.