Image Resizer is one of the many Windows XP Power Toys available for
Free. When you install it all you have to do is right click the photo and choose resize to resize your photo to whatever you need. It makes a copy of the picture so It doesn't destroy the original. Very Handy IMHO and its
free!!!
If you don't have XP ACDSee and several other viewers are capable of resizing and even transforming photos on the fly. So you don't have to invest in expensive programs (Photoshop, et al) to accomplish simple resizing.
Hope I helped you with a resource at any rate.
Note:Off topic, but I highly recommend getting the Power Toys as they add a lot of functionality to your OS, especially the ubiquitous TweakUI. They are available for any OS from windows 95 forward (not all the same Toys).