Microsoft Security Essentials (MSE, codename "Morro") is the new FREE anti-virus software by Microsoft. (follower of Windows Live One Care)
It will protect all Windows systems against viruses, worms and other malware in realtime, without paying for anything.
Moreover MSE runs in the background, so it doesn't have a high cpu usage like other anti-virus softwares.
A dynamic signature service will keep the virus signatur up-to-date.
Security test results:
Wildlist 08/2009 with 3.732 viruses and other malware: MSE detected and deleted all of them
Another test with the latest 545.034 viruses/worms and other malware: 98,44 %
Adware and Spyware detection: 90,95 % (test of the latest 14.222)
rootkit detection: 100% (test of the latest 25)
[url=[/media]http://www.microsoft.de/mse]Download (for XP SP 2, Vista and Windows 7 - 32 bit and 64 bit- )[/url]