Thanks for your help. I read some of this suggestions, but I really don't feel that a "clean" boot is going to help.
"Latest drivers" are a very fuzzy thing for nVidia OEM products installed on Dell/Alienware laptops. They just don't work.
Last thing I did was removing the Win98 Compatibility mode. The game run without "any" issues, except that I lost my saved game (I believe due to some wrong pointer in the registry). I am just finishing the first episode, though. Two more hours to finish the second one, at we will see.