The progrms for spyware and AV I am using are free no purchase required. I will be purchasing a AV when Windows 7 comes out. However the other spyware programs are free. You really can not have enogh protection what one program misses another may catch.
SOme of the other programs not mentioned like Hijackthis and autoruns can also be used to tweak settings and see what crap you have starting that shouldn't be. I have NEVER seen an anti virus do it all!