[face=Verdana][/face]Nvidia Display Card Drivers have an option that allows the user to opt for a (selected) window transparenscy when the nvidia toolbar (at the top of every new page) is left clicked. The degree of transparency can be chosen using the nvidia desktop contol panel which can be selected from the systray or right clicking the Desktop and selecting nvidia properties( NOT nvidia contol panel)

This is a feature of geforce drivers that has been around for several years. It is useful when it works but too often upgrading the display driver causes it to fail and attempting to use it results in a message that the feature is temporarily disabled because some other application or hard ware is using  3D or Direct X. There are many solutions offered,  but in my experience none work for long because there is no way of identifying the offencding application (or hardware)
When the feature is working one just has to left click on the top of a Window whicih then becomes transparent for as long as the mouse button is depressed.

A neat freeware applet "Glass 2K" will similarly manage window transparency but it is not so easy to use. as a hot key has first to be pressed.

My present Windows XP display card is nVIDIA GeForce 8800 GTX but I have had the problem from time to time with cards going back to the 6xxx series .
Does anyone kow how to identify the software /hardware which causes the problem or suggest another way to configre the diplasy do that Window transparency is always available?

   One of the problems with GEForce is that some GEForce driver versions do not work properly with some cards.  Once you find a driver version that works with your card, DO NOT UPDATE.  You can try the different driver versions on their website.