Ad-aware personal is freeware. Here's the link:
http://www.lavasoftusa.com/support/download/
I use both Spybot and Ad-aware. They both find things that each other miss.
As far as junk spam, I never have had a problem on this forum with the email account I used here. I use the email account for other message boards as well, so it has seen a lot of usage. But I don't have a junk mail issue.