It's not going to be a completely smooth ride, since there are some new things that you'll have to put into learning about.
Linux is a unix clone, and so is very different to Windows. Normally, you can't run Windows applications in Linux, but sometimes you can if you use Windows emulation software called WINE. For games which only run on Windows, you can use software called Cedega which will allow DirectX games to run.
Bear in mind, that you'll have to learn a lot, but its nothing too taxing. For a new user, I would suggest Ubuntu, or if you want a slicker looking GUi, Kubuntu. You can find them at
Welcome - Ubuntu: Linux for human beings and
Kubuntu - The KDE Desktop They both have the same underlying core system, the only thing different is the GUI. You can download the .iso files of the latest release (v 6.06) and burn them to CD using software like Nero/Alcohol.
Generally, most of your normal hardware will be supported. This includes disk drives, sound cards (the majority), graphics cards (if you download and install the appropriate drivers). However, exotic, uncommon devices may not be supported.
Check out this FAQ for more information:
http://www.hardwareforums.com/linux-general-faq-8142/