The Grand 2 is not compatible with W7, same as 64-bit OS. So it could works only if you are very lucky.
You can try to run Cubase in 32-bit mode, and in Windows XP compatibility, as experiment (C6 doesn’t support Win XP, but it works, sometimes). And you can try, if The Grand 2 will work this way.
I’ve got The Grand 2 running, Win 7 64, Cubase 6.5 32 bit. There’s an error message while installing from disc as far as I remember, think you need to install from the Grand-update found in Steinberg’s ftp-archive ftp://ftp.steinberg.net/Archives/VSTi_TheGrand/PC/ + copy the sample content from the DVD manually + relocate the samples when using it first.
No chance to get it running standalone but at least as VSTi withing Cubase.