i wanna say that everyone says s&d + Adaware rules,
well microsoft anti spyware should be included along with some other progs such as mcafee or another prog ( which includeds anti virus / spyware ) one of them is norton which isnt my favourite.
Almost no spyware / virus gets through , best of all they're all free ( legally that is ).
Regular updates are included which helps alot, some detailed infomation , and other little bonuses which come with them, such as :
Mcafee security center
Adawares own plug ins ( tweak progs ).
Ive rarely had any problems with a virus or spyware, and for me , thats good.
i use to have about 5 viruses per week.
now its almost 0 per month.