The best, fastest, and easiest small image resizing tool is the Image Resizer Powertoy originally for Windows XP. It unfortunately is no longer supported by Microsoft but a huge fan base keeps it going for newer Windows versions.
It is simple after you download and install the program it adds a line to you right-click options when right-click a picture.
The second screen pops up and gives you a several options to resize the image. It will create a second file for example: original.jpg is resized to original (small).jpg.
While there maybe hundreds of photo editing software this is the best for older computers and Windows machine in general is Image Resizer.
Currently you can get the latest community supported versions at CodePlex.
100% is what I would give this little app and I hope they keep supporting it over at CodePlex.