You don't have to use the built in print screen button, get yerself a freeware utility such as Irfanview, as suggested by Hawk, install it, create a folder in your 'My Documents' section on your c:drive, go into Irfanview, click on Options > Capture/Screenshot, then in the boxes you want to tick -
1) Full desktop area - all monitors
2) Hot Key - I use the F10 button on my keyboard
3) Save captured image as file
4) Destination Directory - browse to your created folder on your c:drive and click on it
5) Save as - scroll down to make ALL your screenshots JPG format to post on any of the Railworks forums, any other formats such as PNG are not allowed.
Then press Start, go into your game and whenever you want to take a screenshot press F10, it'll make a sound to indicate that the shot has been taken and will appear in your specially created folder, afterwards you can then transfer your screenshots to a hosting site such as Photobucket, Imageshack, or, whatever you use personally, I use http://www.mynetimages.com/
, which have always been OK and very easy to transfer your URL of the screenie into the Screenshots section of this forum.