I’ve rarely had any problems with V-Ray and memory usage. The few times I’ve had really large renders I’ve rendered to vrimage and that has worked fine.
If windows 7 64 bit is same as Vista 64 bit then yes the 1.7gig limit will exist but only because sketchup is a 32 BIT APP. There is a small app that I tried and it allowed me to get to 2.2gig before failing so I use that for large renders. Search the forums for it as I dont have the link off hand.