Moved FS and now have a major fps problem...HELP!

[Triple_7]

The other day I decided to back up some of my aircraft and scenery then wipe FS out and reinstall on the D drive sence it is empty and theres more space.  For some reason even with the exact same settings I used to use.  I now get fps of 13 and 15 insted of my usual 25 even.  

Anyone have an idea.  Switching drives shouldn't have made a difference :-/

[EirePlane]

I'm no expert but i would guess it could be:
Something to do with the hard drive's speed and how quick the computer can access the drive.
The fact that it isn't the primary drive
Something else within the game (e.g. new scenery)
something in the system registry