Help return gfxcard mem

AvailVidMem() is cool for returning an AGP cards video memory. However, I'm having issues with my laptop which uses a shared memory setup. The card only has 16 MB available for display. If you set the res and screen depth to high for the display you get strange artifacts all over the screen. Generally I can run the game in 1024 X 768 X 16 but if I go to 32 bit depth even at 800 X 600 X 32 I get strange effects.

AvailVidMem() reports 41 MB which stinks because I'm trying to create a quick profiler so that players won't have to set up their options to get ideal settings for their system (unless they want to tinker).

How can the amount of memory dedicated to the actual on screen display be calculated?

If that's what DirectX is returning, I'd imagine the only other option might be to find it in the Registry somewhere...

What's messed up is that DX Diag reports the 16 MB correctly !?

DXDiag is probably getting that from the Registry or from some direct hardware query, but whatever legitimate DirectX call Blitz makes to get this information obviously returns something different (probably returned from the driver itself).

I imagine I'll be able to find this 'correct' value in the Registry later, though Blitz is doing what it's meant to do... email me so I have a reminder later on!