Irfanview (Photo Editing)

Irfanview is a simple image editing program.
You can download Irfanview here 

The most common functions are cropping and resizing.

To crop an image, highlight the portion you want crop and click
Image/Crop Document (or ctrl-Y)

To resize an image, click Image/ Resize/Resample or ctrl+r

Then select the desired pixel size of the image. 

 For information about more advanced features, look at the tutorials  here here and here and watch a screencast tutorial below.