Just hit "print screen" on your keyboard.
Got to your "clipboard" and save the screen shot to "my documents".
Then use this free editor to turn it into a jpg.
You can only do one at a time.
Or you can do the PRTSCRN - but then simply paste CTRL + V the image into your favourite image editing program.
Id recomend pasting into MSpaint, quick and reliable (on a screenshot basis)