There are several high-quality, free Linux-based operating systems available. I was "rescued" from Vista by Linux and haven't looked back; I recommend you do the same.
If you are a hard-core gamer, you may want to hold on to your Windows, considering most games are developed for use in Windows. There is nothing stopping you from dual booting a Linux and a Windows installation, though; you can find more information on that on the various Linux websites.
I recommend the Ubuntu Linux, which can be found here
You can also try openSUSE, found here
Fedora is also a very well-respected distribution. The author of the Linux kernel, Linus Torvalds, uses it. Check it out here
Or, if you want to see another free OS infinitely better than Windows, take a look at Linux Mint, found here