Windows XP can use a Powertoy, which lets you resize images from the right click menu. This tool was not made available for Windows Vista. In search of a similar tool, I found the Image Resizer Powertoy Clone. Here’s how to do this in XP.
Resize Pictures from the Right-click Context Menu in Vista
After installing the tool, right click any image(s), and click Resize Pictures
Choose your dimensions and click OK