The Snipping Tool is one of the simplest ways to take a Screen Shot.
An example Screen Shot taken with the Snipping Tool:
More It comes pre-installed on your computer and can take Screen Shots in a variety of modes including Rectangular Snip, Window Snip and Full Screen Snip. More information on how to use the the Snipping Tool can can be found on Microsoft's website here..
An example Screen Shot taken with the Snipping Tool: