Parallels does not support 3D gaming nor Aero on any
machine. It does not yet have that capability as it
treats the video card as low-end, and thus, cannot
support the higher based graphics.
So, anyone in this thread that is reporting that they
are actually seeing AERO working via Parallels is mistaken.
If AERO is actually working, its borders would be translucent
where you can see the wallpaper or other objects beneath it.
You can see AERO in BOOT CAMP, but Parallels does not
yet support it through OS X and that is a documented fact.
There is good news....
Word is that very soon Parallels should be supporting high
end graphics so that people can take advantage of Vista's
AERO functions.