Like a lot of you, I've been keeping two or three separate OS environments on each of my PCs for years. Part of this is a natural result of life as a tech journalist, having to test software and hardware in Windows, Mac OS, and Linux. But these days I spend most of my free time in my Linux partition, thanks in part to a little program called Wine.
Wine is a totally open source rendition of the Windows API, built entirely from non-Microsoft code. But to most Windows applications, it looks just like your favorite version of Windows. This low-profile API lets you install and run just about any Windows programs, including games, so you don't have to drop everything and boot into another partition just to get to them.
Because Wine is simply a software API and not a CPU emulator, it uses very few system resources, leaving your PC running lean and mean. Plus, it lets you choose which version of Windows you'd like it to imitate for your applications, from Vista right on down to Windows 2.0.
Configuring Wine for 3D gaming isn't always straight-forward, because video and audio drivers can be wonky in Linux. But with a little bit of tweaking, you can get just about anything up and running.