DX 9 card(hardware, not just software), Pixel Shader 2.0 32-bit support in
the hardware, and WDDM drivers from the video card manufacturer. Depending
on the video card at least 32/64mb has been claimed, but if the card uses
shared memory it needs to be a much larger amount allocated.
It is nothing special, but the software does require these so it can
properly run them through your gpu and not use up more of your cpu time
rendering these effects.
I had an older video card which seemed it met the requirements, but it was
only DX 8.1 hardware, and didn't have the pixel shader support required,
however it sure had 128mb of memory, that was also an agp card... Onboard
video cards have had the most hardware limitations also unless they were
meant to be an attempt at a real gaming card, and then you still needed to
get the special drivers for those cards as unlike normal video cards onboard
cards usually require special drivers.
I have gotten a new video card, basically a used card that met the
requirements, and Aero/Flip 3D is nothing special, it is not worth wasting
any money on at all. If you want to upgrade your video card for the purpose
of gaming, then do it for that, but not Aero, however Vista will not be
released until next year anyway, which is when DX 10 cards will start coming
out also.
Do you need special drivers to run Glass? That would expain why I am not
seeing this.