Driver v185.85 WHQL for notebooks fails to install NVIDIA Control panel fails

I have tried to install 185.85_notebook_winvista_32bit_whql on a Dell XPS M1330 with a GeForce 8400M GS card so that I can use CUDA 2.2. I first installed the Dell BIOS update as recommended.

The installer seems to run for 5 or 10 minutes and eventually finishes with a message that the NVIDIA control panel cannot be installed.

The NVIDIA control panel and PhysX control icons both appear in Vista’s main control panel, but if I try to run them I get an error message saying “NVIDIA Display Panel Extension cannot be created”.

After I reboot I no longer have the Windows Vista Aero interface and Windows Vista Aero has disappeared from the list of options available in the Windows display settings control.

Does anyone have any ideas about what is going wrong here?