Help!

[Ecto Jedi]

I'm working on a review of the 1997 PC game Virtual Springfield for my blog and I was wondering if anyone knew how I could possibly take screenshots of this game during play? I've tried the obvious methods, e.i. hitting Alt + PrtSc while running the game, but the image just comes up totally black. I can take screenshots of my desktop just fine using this method, but I can't take screenshots of the game in progress.

It sucks too that the game doesn't seem to be able to play in any sort of way if it isn't maximized, so that limits my options right there it seems. I'm currently using the image software The Gimp, and that has a screen capture feature, whereby you drag a cursor onto the window of your choice, but I can't use it because Virtual Springfield can't be played in anything but fullscreen. (Or so I assume.)

Does anyone know another way of taking a screenshot? I'd be much obliged if anyone could offer some help.