If you go to Linux, then you gotta consider a few things.
1. Will all the software and games you use run on Linux
2. Linux is VERY different from Windows, it will take you at least a few days to find your way around. Even installing software is different, as some software will require you to recompile it's code so it runs on your Kernel version.
3. Which version of Linux are you going to use. Because Linux is open source, there's soo many different versions around. Not only that, the people who run Linux themselves have their own favourite versions. I have found that the so called "Linux Experts" can sometimes be unhelpful, especially if you're using a different version to them, and I get the feeling they feel Linux is a bit Elitist.
On another note, If more of us moved over to Linux, it would obviously become more popular, and the more popular something is, the more people like to target it. So Linux would get a whole new batch of viruses of it's own!!!
My advice is stick to Windows XP SP2, keep the updates up to date, get a good virus checker and some good spy ware removal tools. Don't forget to keep them up to date too.
Also, when surfing the web, NEVER click yes to popups that ask things like "Do you wish to install"
I have been running Windows XP on this machine for over a year now, and it's still as solid as it was when I first installed it! That's another point, I'm not trying to sound condescending here, but if you haven't got the computing skills to keep your Windows machine virus free and functional, then I would stay well away from Linux as its much more complicated and not as friendly as Windows XP.