Hi,
I'm using the 94.24 nVidia drivers on my 6600 GT.
That runs Trainz 2004, 2006, TC3 and TRS2009 (Beta2) quite happily (it dod create the warning message - but I ignored it).
If I update from this version, I have another simulation that crashes on exit so I'm staying with the old drivers.
Look on the nVidia site for the driver archive!
HTH,
Colin