When BigBeast (XP3) was the flying machine, I had three FS9.1s installed, and thanks to a huge collection of freeware landclass, meshes and coastlines, I could use VFR pilotage to navigate from the UK to Oz, or all over Europe, from FL210 in a Connie or DC-7C, or 8000' to 12,000 in lesser, non-presurised machines....Australia? - bear left at the Pamir Knot; that's my kind of navigation
Sad to say, Win7 does not seem to take kindly to multiple installs on the same drive, even though each has its own language.dll; I kept seeing things which were specific to a different FS9.cfg from the one I was flying in.
On the current flying machine (SuperBeast, Win7) FSX is in C:\FS10 and FS Classic is on its own drive, at G:\Classic FS. That will do for now.