I have exactly the same hardware id as Vaio 77 above post:-
Sony Vaio VGN-AR51E laptop.
I have just upgraded from vista 32 to Windows 7 but took across all my files and settings - did not do the clean install. Well I have pasted your NV_DISP.inf in the NVIDIA driver folder for the latest desktop driver 191.07 and followed your instructions to the letter. WellI get an error message at the end:-
"Windows found driver software for your device but encountered an error while installing it.
NVIDIA GeForce 8400M GT.
The system cannot find the file specified ."
I wonder what you could suggest?