There's some good free packages out there, you don't need to pay for it.
Avast antivirus, Adaware, and Spybot S&D are the only protective
programs I have, Firefox is a much more secure browser than IE, so it's
the only one I use except for sites that require IE, and of course the
best line of defense is the user. It goes without saying that you
shouldn't visit sites hawked by spam, give out your main email address
to unknown recipients, or open attachments that you are not absolutely
certain of.

You have to be really careful about phony spyware protection products,
websites that claim to "scan" your system, find infections, and then
sell you worthless software that you don't need. I see a lot of people
in my parents generation falling for these and have spent a lot of time
cleaning up infested PCs and educating clueless users.