There's loads of these things around...
BB FlashBack Express - http://www.bbsoftware.co.uk/BBFlashBack_FreePlayer.aspx - good screen video capture program. Captures to AVI and SWF formats. The problem with this one is it puts a halo around the screen cursor which cannot be removed.
Expression Encoder - http://www.microsoft.com/downloads/en/details.aspx?FamilyID=5c3c5f97-678c-4c99-a7fc-f84f320c626f - An advanced audio/video-encoding and live-broadcasting application. A huge program but the video capture is great. Captures to WMV format. The free version is good enough for most things but the free version can only record 10 minutes segments. The paid version is $600 but it is absolutely fantastic. I've never had a problem with the audio desyncing from the video when using it.
Screen to Video - http://www.koyotesoft.com/indexEn.html - great screen video capture program. Can capture screens to AVI, SWF, FLA and WMV formats. My favorite free recorder for general use.
Wink - http://www.debugmode.com/wink/ - A tutorial and presentation creation software. The screen capture is great. Captures to SWF format - another good program from the maker of Wax video editor.
The most common one is Camstudio - http://camstudio.org/ - but I stopped using that some time ago because of problems with it unable to capture subtle gradients and it even changes some screen colors. It was whilst looking for a replacement for that that I tried about 30 of the screen recorders and came up with those 4 above.
Camtasia - http://www.techsmith.com/camtasia.html - is very good but it is $300.
Fraps - http://www.fraps.com/ and http://www.bandicam.com/ are both OK and are less than $40 but both are a bit heavy on resources.