You can change the size of the video using Windows Movie Maker. See this link:

http://www.papajohn.org/MM2-SavingMovies-CustomProfiles.html

I would recommend getting the older windows movie maker 2.1 which has more features than the one included in Vista.
http://www.microsoft.com/windowsxp/downloads/updates/moviemaker2.mspx

You can also use VirtualDUB:
http://www.virtualdub.org/

good luck,

FlyerX