Hitting "Print Screen" while you're in the desktop does it. Then you just paste (ctrl+V) it and save it in windows paint. Then the upload is similar to that of any other pic.
Wow Petrarch, a perfect wallpaper for a scholar . I see you're using Vista. Since I'm not much into programmings that i heard it hampers, I too have used it for a few months and liked it. Till last month, when I had to switch back to XP because having multiple user accounts in Vista slows my PC down. I miss that notepad very much!