my boyfriend erased a bunch of files and system folders from my g5.he memorized my IP adress when i was trying to connect to the internet with my airport to the only unsecured network available in my neighborhood(signal is really weak and i don't know who owns it) and from his laptop he got access to my imac and messed everything up maybe using remote desktop or something like that. my question is, after i reinstall osX on my computer, what do i need to do to block him from getting into my computer remotelly from his laptop?