Hmmmm, I've not heard of screenprint not working on a browser. Try this out just with anything on your browser window (like this forum!) Hit the PRTSC button in the top right of your keyboard. It won't "do" anything that you can see, but the image of your screen should now be on your clipboard.
Now go into Start - Accessories - Paint (or whichever paint program you have) and make a new empty file by doing File - New. Then you should be able to do edit - paste to paste that image into the file ...