Watermark is little information shown on the bottom left corner of the desktop.Watermark is only shown on RC Or Beta copy and it is removed from RTM builds.
Some guys love watermark as it shows the information about the windows right on your desktop and if you are using RTM copy of Windows Vista Or Windows 7 then you must be missing it because by default it is removed.But here is a trick from which you can get Watermark on your RTM copy.
Just follow these steps:-
Open your registry editor by typing regedit in run command,
Now navigate to:-
In the right hand pane look for the entry PaintDesktopVersion,double click on it and change its value to 1
Now restart your machine and you will see your watermark there.
To remove it just again set the value of PaintDesktopVersion to 0(Zero)