Wow... An easy way to solve this. If you want his IP simply send him a file, when the file begins it's transfer go to Start then click on run, type CMD and hit enter. In the command box type netstat -a to have a list of all active connections to your PC.
There should be a hostname in that list, once you have the hostname go to Google and look for a hostname to IP convertor and convert that hostname into the IP.
There you have it, his/her IP...