I have the solution!!!
Check and install "Omega Driver for NVidia"...
In the next link chose your OS and download...
http://www.omegadrivers.net/index.php?option=com_phocadownload&view=section&id=2&Itemid=55
To install, first uninstall your video drivers, reset, and install it...
My full shadows are now available again!!!!
It works for me, my system is AMD 3200+ ; 1536mb 400Mhz RAM ; 7950 GT AGP GDDR 3 512MB....
:)