I've been using AVG AntiVirus for a long time now, and I must say I love it. For one it's free forever, no subscriptions or other crap Symantec will put you through, and no up-front costs that McAffee will put you through. Considering the only other person using my computer is very very apathetic (doesn't care, for all you lazy folk ;)) when it comes to security (and I quote: "They're not going to hack our computer! They have no reason! Why would they want to? It'll never get hacked into, I promise.") and it has caught many viruses that the other person has opened as email attachments (quote: "It was from someone I knew!"). Sure, it may not have all the bloated features of Symantec's or McAffee's a/v programs, but it works just fine for me. Manually updating the virus definitions is a little awkward, but I just noticed a little automatic updating function, so that's cool.
Give it a try, and give them your real email. They send you a code you have to input during installation (copy+paste from email). Don't worry, they won't spam your email.
You might also try Pest Patrol. It really isn't an anti virus program, but it works very well against spyware, of which there are probably numerous examples on your computer right now if you don't have a dedicated spyware program installed.
Instead of giving them your real email address, I suggest that you set up a new, crap account that you'll never use again and have the download link sent there instead. I gave the name "your mom" when I signed up for it and now I get spam addressed to "your mom". Other than the spam, I love AVG.