Go to my library and download the file called image resizer powertoy, its very small.
It is an add-on to windows explorer. After you run/install it, all you do is right click on the image(s) that you want to resize and one of the options will be resize image(s). Be sure to click on the advanced button, it will give you the option to keep the old large files and create new files or just keep the new files. It will also allow you to change only larger files to small without changing small to larger.
This is an amaziangly easy little utility that should have been included with XP but is not and an absolute MUST have for anyone who owns/uses a digital camera. You can do one image or thousands at tonce. Give it a try, you'll see what I mean.
Gerry