Microsoft offers free download of a Windows XP Image Resize Powertoy on their website. PowerToys are utilities Microsoft programmers created while working on Windows. This powertoy lets you resize a photo in seconds with a simple right click -- perfect for preparing it to upload on wikiHow!

[edit] Steps

Download the image resizer powertoy. Go to the Microsoft page in external links (below). Click on the download link along the right side of the page for Image Resizer.
Install image resizer. Double click on the .exe file and follow the prompts for installation.
Find an image you'd like to resize and right click on it.
Select Resize Pictures from the menu.
Select a pixel size you would like to resize to from the menu. If you click the Advanced button, you can select a custom size. Enter a height and a width in pixels, and the utility will shrink the file to a size that fits the more restrictive of the two dimensions while keeping the image correctly proportioned.
Unless you select otherwise, the resized picture will be saved in a new file in the same folder on your hard drive.