Changing the resolution of your digital pictures to send via email or to post items for sale on eBay or Craigslist is easy. If you have just a few, you can use any draw or paint program that can import JPEG images. Just open the image and save it again (use Save As) in JPEG format. This will reduce the size of the image. However, if you have a lot of images, you can easily do that with Irfanview, free software you can download and install in your computer (http://www.irfanview.com/main_download_engl.htm).
You can also crop, enhance, sharpen, rotate, resize and apply effects to your images.
The FAQ section of their Home Page and the Help menu both have instructions on all the image editing features.
Download and enjoy!