From my experience, people who steal others gaming accounts do so with keyloggers and trojans, being the script kiddies they are. I play Starcraft and a lot of other games and i always see people advertising their "hacks" and "cool l33t progZ!" which screams out OMFG TROJAN!!! If youre friends with this guy im guessing youve probably chatting outside of the game, perhaps on aim/msn/yahoo. And if he started talk/direct connect/file transfer he can get your ip, or if you accepted a file it may have been infected with a trojan or such. He might of even attacked it with a dictionary attack, which isnt likely but possible. So as everyone has said three times over, close up your security holes, and if you try to hack it back (revenge keylogging doesnt fall under this but under idiot manuvers) you can get charges pressed if he does not turn out to be a kiddie. If youre still infected, even if you do hack it back or whatever you expect to do, you will lose it once again! Oh the cycle! So: Antivirus, firewall, ShieldsUp, RegMon, FileMon. These will all help you in cleaning your system. Sorry if this is just a bunch of rambling but i just got back this week and i was excited to post.