For gaming and other 3D accelerated stuff, Fraps is hard to beat. For just plain desktop recording, VirtualDub is my tool of choice. It does way more than just screen recording, but among it's many functions are video capture from any device, including the screen itself.
If you have a Mac and running OS X Lion (That's what my laptop came with, so it may work on earlier OSs, too), there is a feature built into OS X Lion that allows you to record.
To access this, go to Quicktime, go to File, and select "New Screen Recording." From there, your screen should record once you hit the nice record button.
Now, in terms of Windows, I've really only used FRAPS. Sure, the price is steep, but it's really good software. I haven't tried it on a quad core computer (I've only used it on a Pentium IV), but it should run quite nicely. However, if your game allows demo recording (Source Engine powered games can do this), set it to record your gameplay, and it shall record everything you do, sans your own voice. Then, you can set it to render frame-by-frame, so you can get 30FPS or greater, depending on what you want to do, even on settings your computer couldn't handle.