My computer is network 2 how do i find address of network 1

Hello, I had a person give me this computer. He installed me as network 2 to share the desktop - I would give him permission via Skype to help me with problems when encountered. We since broke up, but I still have network 2 internet access showing. My question is two-fold: 1) I know he would NEVER purposely harm the computer he gave me, but is there any threat to me just by it being there? He installed some card into the hard-drive. I'm obviously not computer savvy & don't understand the lingo. 2) I really want to get a hold of him. He is hiding behind 3 proxy servers, under the guise of being a business. I called them, but none would give me info. He also changed his phone number and moved. I know he lives in Toronto and uses Rogers Cable. I have no one to call about him or I would have by now. Thanks - he's also an IT Pro - very clever guy. I'd really like to outsmart him.