If you're interested in games, stick with Windows. No other operating system comes close when it comes to games... for now anyway. Mac is getting there, but a lot of games still only come out on Windows.
However, if you have absolutely no interest in games, I'd go with a Linux OS. For many reasons:
1. Most (if not all) of your current hardware should work in a Linux OS.
2. Aside from games, Linux can do most anything else you'd need to do in Windows. Surf the net, create documents (with OpenOffice), chat on messengers (Pidgin works with both MSN and Yahoo, but there is aMSN (a nice MSN clone) and Yahoo's Linux client.
3. Linux distributions can support the NTFS, FAT, and FAT32 files systems that Windows uses, meaning you can still use memory cards, flash drives, floppy disks, and CDs that you already have.
4. Most Linux distributions are FREE. While most of these lack official support from the makers, there are massive communities for each distribution with many knowledgeable people who can help you should you need it. There are PAID versions of some distributions that offer official technical support as well. These vary in price and you can usually pick one up at your local software shop.
5. Most distributions come with (or you can download for free) OpenOffice. With OpenOffice, you can still create Microsoft Office compatible files and view documents from other people. The only problem is with the new Office2007 files. As far as I know, these can't yet be opened, but I expect support will eventually be added for them.
6. Many Windows programs will work with an add-on for Linux called Wine. It simulates a Windows environment for those programs so they can run in Linux. It also works for some games. It won't work for everything however.
7. Less demanding for resources than Windows.
I could go on, but I think you probably get the picture.
A few negatives on Linux:
1. Many distributions don't come with built in support for media files (like MP3, WMA, WMV, and DivX). However, support for all these types can be added.
2. Many games, especially 3D games, meant for Windows won't work well (or at all) in Wine for Linux.
3. Lack of official tech support for most distributions.
4. Some hardware won't work properly in Linux (such as Philips webcams (by design
)).
On picking a distributions, you have to take your needs into consideration and pick one that suits your needs. Fedora, Ubuntu, Debian, Knoppix, and SUSE Linux are some of the more popular ones. If you're just starting out with Linux, I'd go with
Fedora or
Ubuntu. Both are fairly easy to use (compared to others) and both have huge communities.