ad-ware problem

my roommate has a serious ad-ware problem (i sware its my friend, im too paranoid to get that on my baby). anyway, i told him to get Firefox, and he did. the problem is he still gets ads and ads and ads. they all open in IE instead of mozilla. is there anyway to block IE.exe from opening as a whole? i dont think deleting it even works, and i dont think it would be good anyway.

any help would be rad, or maybe even a really good ad removal software (needs to be free! -money's tight, gotta pay rent... and smoke the rest)

"If you still got bullets, keep shooting"
http://www.uncleardesign.com/