I'm using AdAware,SpyBot S&D,Microsoft Antispyware,SpywareBlaster.
I think that one the best if not The Best is SpySweeper.
Once I had some nasty crap infected my system, nothing helped.
Downloaded trial of SpySweeper - got rid of it. But it's not free. They have a special now for $15. Highly recommend. BTW, it's one of the top downloads on Cnet and everywhere.
Another piece of Free software I recommend is MyUninstaller.
It's just excellent - what Norton can't uninstall or leaves pieces behind, MU does a complete job.