Microsoft's free antivirus, Microsoft Security Essentials (MSE)
My Norton is about to expire, and MS just released MSE the day before yesterday, so I quickly gave it a try. Microsoft Security Essentials (MSE) can protect computers running Windows XP, Vista, and Windows 7 against viruses, spyware, rootkits, and Trojans. The Microsoft Security Essentials software itself cannot fend off all web threats, but when used with the IE8 browser and a fully updated Windows operating system, it will provide users with a complete security solution.