If you want an excellent, free, and basic Anti-Malware software suite you can get it now from Microsoft.
http://www.microsoft.com/security_essentials/
I have been using MSE for a while now and I have to say it’s exactly what I want in an anti-malware solution. It provides first rate protection against all types of viruses, spyware, adware, trojans, and rootkits. It’s free forever, and it just works. It’s unintrusive, works well in the background and doesn’t take up very much system resources at all. In fact, you’ll barely know it’s there unless you take a look every once in a while.
I highly recommend MSE for basic (and free) anti-malware protection for Windows-based PCs.
Note: If you can’t stand the idea of Microsoft AV, or you WANT to pay for anti-virus software I recommend the following:
