Try the microsoft home page. One of the PowerToys for Windows XP is an Image Resizer. It's great! A standard reduced size is for a pocket pc sized device.
http://www.microsoft.com/windowsxp/p.../powertoys.asp
I use it all the time for this and for shrinking images for easier emailing.
(I'm assuming you're using Windows XP. If not, you may need to keep searching.)
Good luck.
-- ADG