That's how I do it with a fresh Windows, if you have W7 installed and made 2 partitions:
Do not connect any old HDD while installing W7 just the new one! To keep the C: and D: partion names fixed!
Make c:\ ~ 100GB for W7 and a d:\ with the rest for the data
After installing W7 just install all the drivers I mentioned above, then connect to the net and let W7 install all updates!
Install GEM+ into C:\GPLSecrets
copy GPL into d:\GPL
There is no reason why GPL should not work in your new system. I installed, or passed GPL from one PC to another many times. This is what I do :
1) A fresh installation of GEM+ (must), if I install GPL for the first time in a new PC
2) A fresh installation of GPL with the latest installer, directly in the main driver :C/Sierra. (Not strictly necessary. I could also just copy my GPL folder from one PC to another)
3) Replace installer's tracks, cars, sounds or other folders with my preffered ones
4) Install new mod
5) Launch GEM+ and point to the rigth directory of (GEM) GPL!
If I need to install GEM+ for a second time, I make sure to have deleted or renamed my previos GPLSecrets folder and there are no other sgem.ini file somewhere else.
Btw, while writing I am thinking that there is the GPL installation step by step guide, prepared by Stephan explaing in detail some if not all, of the above points.
Good luck.