Since I installed Windows 7 beta on my Dell D830 laptop I was not able to get Aero glass as my current driver only support 16-bit color. Moreover the nVidia beta drivers for Windows 7 available on Windows Update refuse to install for me.
So I was stuck for a few days until I found this on a TechNet forum:
Right click on desktop
Select NVIDIA control panel
Select Display / Manage custom resolutions
Click "Create...", enter 32 for "bits per pixel"
Click test and save it.
The test reports a failure but... it works!