Earlier versions of Windows had a resizer in the powertools. It was left out for Windows 7, but this is a good replacement -
http://imageresizer.codeplex.com/releases/view/30247
Just download and install it. Then you can select as many jpeg files as you want, right click, and in the menu you will get an option to resize pictures. You can select to have it keep both the original and the smaller file, or replace the original with the smaller file. I use it all the time. It's much faster than using paint. There are several options for size - I use 'Large' and it's still small enough to upload here.