Apologies, I should have made it clear that I know how to use print screen - but as it should have been clear from the fact that I know of the old trick to take screenshots, I thought it rather pointless to mention
Sadly, taking a normal screenshot isn't working, which is why I posted. I'm getting ye olde 'black screen with lots of sparkly odd bits scattered over the screen' bug.
Playing with free download version in 800x600. So far tried paint and photoshop. Not getting anything but the bugged picture.
Thanks for the info on full screen. Will go hunt down a direct X capture programme and see if running it in full screen will get me some screenshots.