If you only want to get one screenshot you should be able to hit the PrintScreen button, exit or Alt-Tab out of the game, and paste the image into a graphics program.
Alternately, there are programs to automatically save screenshots. I use
PNGShot, but it hasn't been updated since 2003. A couple others that I saved links for but haven't gotten around to trying yet are
Gadwin PrintScreen and
MWSnap, or check out some listed
here (I have not tried fraps, either).
