For those who have GRAW2 take a gander at this
C:\Users\(name)\AppData\Local\GRAW2\settings\profi les\graw2_(name) (different in xp)
called settings.xml that contains these settings (among others):
<has_physx value="false" />
and
<physics value="0" />
to enable the full detail of physics, without an Ageia Physx card:
change the <physics value=> setting to "1" ("physx high") or "2" ("physx Extreme"), depending on your system, go to the graphics options while in-game and change any random setting (don't really have to change anything, just click something so you can click on "Apply"). Then click Apply and enjoy a visual feast of 3d pieces of dirt flying up when you shoot the ground, amazing explosions that are followed by a rain of soot, and wooden boards exploding into a rain of chips...
make sure you go into the graphics menu AFTER loading the level or campaign because it ctd's if you do this from the main menu.
interestingly, when i set the has_physx value to "true", i got an fps boost (made the 2 physics value actually a little more playable).