If you want good antivirus software, look at ESET's NOD32 Antivirus System.
No antivirus is perfect, but it certainly beats going without one.
bmp!
Malware is a fact of life and you have to be proactive in defending yourself. Windows 7, if setup properly, will handle malware as good as any OS, including Apple's.
I defended myself proactively by buying a machine with Unix OS on it. That is, I got a Mac. . . .