This depends on what programs you have installed, more so than what version of Windows. Windows has not got much in the way of image editing.
For starters, open My Computer and find the file you want to edit. Right click on it, and click "Open with". You'll get a list of programs that can edit that file. Maybe you already have a program installed that's capable of resizing the image.
If you don't have a suitable program, you can get Photoscape or IrfanView for free.
Photoscape:
http://download.cnet.com/PhotoScape/3000-2192_4-10703122.html?tag=mncol;1IrfanView:
http://download.cnet.com/IrfanView/3000-2192_4-10021962.html?tag=mncol;1Either of these programs will let you resize images and also crop them, adjust color and brightness, etc.