For Vista

If you want to take a screenshot with windows Vista, theres a not so well known application just waiting to do the job for you.
  • Click the Start Menu,
  • Then where it says 'start search' enter 'snipping tool'
  • You should see the program.
If you use it frequently, right click on it and choose 'Pin to start menu'


For Windows XP

You can take a screenshot of your entire desktop using the PrtScrn button on your keyboard, or for a single window :
  • Click the window in question
  • Press ALT + PRT SCR (prtscr is towards the upper right of your keyboard)
  • Click Start
  • Click Accessories
  • Click Paint
In Paint,
  • click on Edit
  • then click Paste
You can then save the image, there may be an easier way but I havent used XP for quite some time now...