I use SpyBot, AdAware, SpySweeper, and SpyHunter. Every one of them finds something different, none of them cover it all...
And when asshats get on my computer, for some reason, they are able to download and install audacious amounts of spyware, software, and hijacks. Which is why I try my best to keep anyone from my computer. Over my 2 week absence, my sister's friend used my computer, my desk, my notepads, and filled my empty trash can half way with notes scribbled about email addresses and phone numbers on every page. Not to mention, she somehow installed ~30 programs, installed 6 printers, and left my computer with about three seperate hijackers... I fixed them, took a while, but I trailed it all down...