Since last Fall, Microsoft has offered a free program that offers Virus, Spyware and Malware Protection for your home PC. Yes, free to download, free to install, free updates (and not just for 30 or 60 days) - totally free.
Microsoft Security Essentials is available on the Microsoft Web Site at http://www.microsoft.com/security_essentials/
And, if you have used Microsoft Forefront Client Security for your business computers, MSE will look very familiar - they are very closely related.
So, if you haven't been offered anything free that didn't come with strings attached, try Microsoft Security Essentials.