Well, when I try and take pictures of Painkiller; either using Printscreen, or the capturing icon on individual picture programs, it doesn't work. It either just comes up with my desktop background, or comes up as black.
Thanks :)

F12 is the default screencapture key in Painkiller. Saved screen shots in [your drive letter]\:Program Files\GOG.com\Painkiller Black\Screenshots.
Make sure you have not reassigned the F12 key to some other function.
I don't believe PrtScr key will work for several reasons (video card won't pass certain kinds of images which effectively prohibits you from recording / screenshots of movies etc)., a dedicated screenshot program can do the job, seems I used HyperSnap at one time. Had to enable a certain function in the program but it worked on almost everything. Painkiller has it's own screen capture so . . .

Try FRAPS.

Thanks! But it just saved it as tmp.000, nothing else.

You might try the FRAPS program that Namur mentioned above.
I used HyperSnap, ver 5, which had some features disabled (had to reset the high res every time etc) but ran forever. I think the ver 6 has a trial period as well but it stops working after so many days if I remember correctly. It worked well, start before game and hit Insert key (might be wrong on that) every time you wanted a screen shot.
The DRM is built into the video/sound hardware and OS in an effort to stop coping of copyrighted material. Just tried it on my Vista install and got the same results, temp.000. Must be Vista?? Sorry, hadn't tried it on Vista until now.

Yep, might just do that :) Thanks everybody.

I found and installed HyperSnap 5, it does not work on Vista. Apparently DX10 closed the door on the program. HyperSnap 6 may work but I have never tried it. If you find a method, post back for others.

There is a free version of FRAPS that lets you take pictures, but only in .bmp quality. Which is fine because it's uncompressed, so you can just convert it to .png or .jpeg.

I don't believe so, I used the trial version of ver 5 because it never expired. When ver 6 came out it had a 30 day limit ( I think) on the trial and then stopped working. Since v 5 worked so well, I never upgraded to a paid version, just stopped using it finally.
I really like the program, worked great, lots of features, would be the first one I look at if I ever need screen capture again.
You might search the internet for ver 6 . . . . . . . . . . .
@Kingoftherings I agree, FRAPS is great . . . =^ )

you know , xfire permits taking screenshots as well.
chances are you have xfire ;)

They're stored in painkiller black\data\screenshots.