Howie's Quick Screen Capture works for me. Get it free, free, free at
www.howiesfunware.com under Miscellaneous Software. It's at the very top. Download it to your desktop. Put a check in the box to capture only the active window. To use, just double-click the grinning computer icon, then minimize it. It runs quietly at the bottom of the screen in the toolbar down there and when you want to grab a screenie, just hit F12. You'll hear the sound of a camera shutter and motor drive. That tells you the screen was taken. If you are flying over terrain with lots of detail, you will find that the terrain sometimes gets captured but not the airplane. Take more than one if you have doubts. All your screens will have the same folder name with consecutive numbering. Just rename for each subsequent screen-grabbing session. All of mine are saved in My Documents, in the FS Screenshots folder and are named FS-screenshot-XXX; I just put in a different number and maybe a letter extender (XXXx) if I have a lot of similar pictures and I have no duplication problems. Howie's screenie tool is a good little program; try it.