Why go half way? Get partition magic, shrink the active partition, install MEPIS LINUX on the new empty space, and never again have to worry about (not an exhaustive list):
1) viruses
2) adware
3) worms
4) malware
5) malicious activeX scripts,
6) what I affectionately term as "winrot"... that collection of broken links, corrupted dlls and general crap that make reinstalling windows a repetitive affair every six months.
Try it, or Mandriva, or Ubuntu, or Red Hat Fedora. You will never go back.
I've never had a virus or spyware. I don't have to worry about any of that stuff. I've been a Mac user for 10 years. The only time I ever install the operating system is when Apple comes out with the latest and greatest. Mac OSX is great.
I do have to suffer with Micros**t XP at work, however. The Firefox I use at work is considered contraband , non-approved software that could get me in trouble, but I refuse to use Micros**t Exploder.