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:
self-built i7-4790 at 4 GHz; GA-Z97X mobo; GTX 970; 16GB gskill;
Win 7/64: 840 EVO OS; 840 EVO (500G) game drive;
Win10/64: 850 EVO (500G) for OS and games
quiet, fast and cool running.