Yep- give it a try wivelrod.
I think it wouldn't work so well with a CRT monitor as the curvature of the glass would mean the light was not so polarised, but I havn't tried it.
Turn the polariser until the screen turns black, you have now blocked all straight on light and you are left with only light that has been refracted. I made a white screen in PS (try not to get the tool bar in view as I did with the cd case -lol ) Message edited on: 06/22/2005 11:45

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html