In the system tray, the icons next to the clock, right click on the magnifying glass and click on "Desktop Search Options". Once you're in the options screen, on the left click on General. On the right, bottom of the window you should see it say About Windows Desktop Search under that it will show the version number.
The post above was before WDS 3.0 was released. And you're right there is no General Tab in WDS 3.0, I don't know why Microsoft didn't put a button to show the version. So, you must have 3.0.
WDS Version
Jens K. Suessmeyer - MSFT
In the system tray, the icons next to the clock, right click on the magnifying glass and click on "Desktop Search Options". Once you're in the options screen, on the left click on General. On the right, bottom of the window you should see it say About Windows Desktop Search under that it will show the version number.
HTH,
DJV
KitWest
Canderson