Some diseases are resistant to one drug and require a combination of drugs to cure the patient TB for instance.
Spyware is simular therefore if you use a combination of Antispyware you should get of it.
Spywareblaster as a blocker
Defender (XP only) as a realtime scanner
and Adaware as a backup scanner
Works for me not seen any spyware for the last year or so.
Also use a different combination on my networked PCs they alos ar clean.