Personally, I never used
http://www.fraps.com/ myself, but my friend tells me it's good. However it's only for trial.
Back in the days, I used to use SnagIt. It has region capture, you just select a specifil rectangular region of the screen that you want to capture.
It was free, BEFORE... Alas it's no more. But there's also a trial.
www.SnagIt8.info
Try it out. Oh, and don't forget to share!