you should have a fresh backup default copy in your install folder - there is also a copy on the install disk you can get to it directly at:
disk1\program files\microsoft games\Flight Simulator X\scenery.cfg
if you use either virgin cfg, you will have to "add" your scenery back again.
Hooked since FS4... now flying: FSX Acceleration on Win7/64, Core Duo E8400; GA-EP45-DS3R; GTX 460-768MB; 4G RAM; Freezer 7 Pro
in the assembly stage and rarin' to go...
self-built i7 4790 at 4 GHz; GA-Z97X mobo; GTX 970; 8GB gskill; 840 EVO OS; 840 EVO game drive; Win 7/64
... if it don't 'fly' then there's always Tiddlywinks...