The Pc version I use is the one that is available from Microsoft. It becomes a context menu item, so you go to my computer, right click on the image and one of the menu options will be Resize Image. you can resize the image or create a resized copy. Also free

XP version - http://www.microsoft.com/windowsxp/Downloads/powertoys/Xppowertoys.mspx

Open source version for Vista/Win7 - http://sourceforge.net/projects/phototoysclone/