For simple resizing, the easiest to use is a program that is free. It is "picturetray" available at picturetray.com. It is a very small program (300K) that installs in its own folder and installs no DLL's and makes no changes to your registry. Download it, unzip it in its own folder, and run it. If you don't like it, delete the folder and it's gone. (If only Microsoft's programs were so user friendly)
It will allow you to resize, rotate, compress, and save in a variety of formats. It has two panels, you drag the images to be resized to the left panel and then drag them off of the panel on the right. (or copy them from the temp directory it uses) It has its own viewer (double-click on an image in one of its windows) and shows statistics when you hover your mouse cursor over an image.
I use it all the time when posting images to the web or e-mailing them to others and it really helps. Did I mention it is free.
Joe L.