Replying to spyware

hey, whats the best program for finding and deleting spywae on computers? macs? pcs?, are there any free ones that work?, and a friend of mine claims shes getting them through AIM, is it true, if so, how would you block them? i know its probably been posted on before, but hey, i dont care, i am to lazy to look it up. any help is greatly appreciated.

'Really, I gotta say that I'm glad you exist, 'cause if there wasn't there'd be noone to make fun of and diss.'