One of the best tools that I use from windows 7 is the Snipping tool. It is located in the accessories folder. My recommendation is to right click on the shortcut and pin to your task bar. I know there are many free screen capture tools but this one does the job and is always there for you in windows 7 or 8. This is especially useful to send error pop ups to your favorite Tech person as a visual aid to describe your problem.
Snipping Tool captures a screen shot of anything on your desktop, like a photo or a piece of a webpage. Snip a whole window, a rectangular section of the screen, or draw a freehand outline with your mouse or tablet pen (or your finger, if you’re using a PC with a touchscreen). Then you can annotate, save, or e-mail the image using buttons right in the Snipping Tool window. There is also a nice highlight tool to help point things out.