i use a macintosh G4 and my Roommate uses a PC and itunes.
He turned on his computer, and he got my music that I downloaded from Limewire onto his itunes player.

I wired my apartment building so that about 7 apartments all share DSL.

Is this a security issue that I should be concerened about?
How can I stop my music ending up on someone elses computer?
Please help.

thank you.

not a security issue--they can't modify your files.

Looks like you have iTunes sharing turned on in the iTunes prefs, and the preference to make a playlist is set in the LimeWire prefs.

Turn the prefs off if you are worried, but it really is a cool feature. Better yet, tell the others to turn on their iTunes sharing prefs, and enjoy.