Give it a go..... its free and fully supported by Microsoft.
About Microsoft Security Essentials
Microsoft Security Essentials provides real-time protection for your home PC that guards against viruses, spyware, and other malicious software.
Microsoft Security Essentials is a free* download from Microsoft that is simple to install, easy to use, and always kept up to date so you can be assured your PC is protected by the latest technology. It’s easy to tell if your PC is secure — when you’re green, you’re good. It’s that simple.
Microsoft Security Essentials runs quietly and efficiently in the background so that you are free to use your Windows-based PC the way you want—without interruptions or long computer wait times.
Learn more at the Microsoft Malware Protection Center
Find information, definitions, and analyses of all the latest threats that Microsoft Security Essentials can help protect you against in the Microsoft Malware Protection Center
Need security for your business?
Protect your computers with Microsoft Forefront Client Security
*Your PC must run genuine Windows to install Microsoft Security Essentials. Learn more about genuine
ps; I'm using it with Win 7 - MS Security Essentials does not interfere with online games.