This is also from www.lifehacker.com and here is their description....
This is also under the GNU Public License and is also said to be portable...it creates a .ini file after you close it as well so it does seem to be portableDropcloth is a simple application that overlays a solid colored window on top of your desktop. Especially handy for clearing your desktop for screenshots and screencasts, or just getting rid of all the distraction in front of you so that you can focus on just one application without closing out of anything or clearing off your desktop.
Its windows only and it says that it has been only tested in Xp but should work in vista...i will test it on my school Windows 2000 computer tommorow...
Here is the linkhttp://lifehacker.com/software/distract ... 245774.php