Managed to get this working by doing the following:
I took a guess and found that NVSM.INF from the latest 64bit nvidia drivers
was the closest match. So I added:
DEV_01D8&SUBSYS_81E6104D "NVIDIA GeForce Go 7400"
to the nvsm.inf section in the extracted listdevices.txt section.
%NVIDIA_G72.DEV_01D8.6% = nv_G72, PCI\VEN_10DE&DEV_01D8&SUBSYS_81E6104D
to the nvsm.inf.
At the moment all is stable and working on Windows 7 Home Premium 64bit !