If you have FSX on the same drive as Windows, and are
adding the SSD for FSX, it can be easily moved.
Flight 1 has
FSX/FS9 Registry Repair Tool to correct the Registry's addresses after the move.
Copy/Paste it, in it's entirety, to the SSD. Run the repair tool.
After the Registry is repaired, and the new location is verified to perform, delete the original, or, better yet, keep it as a recent back-up.
Any *.cfg or other files that reference add-ons that are not located within the FSX main folder, will need those addresses corrected if their drive letter is changed.
If you are replacing the Windows and FSX drive, a reinstall is best. I've tried many cloning tools and have had limited success, so, a clone may work...may not.
My new rig got a fresh install of FSX Acceleration, but, a complete copy from my old PC was pasted on top of it. Viola! Nothing lost.
Other files you may want to preserve(Win 7 locations):
fsx.cfg and GrantedRewards.BIN, {C:\Users\User Name\AppData\Roaming\Microsoft\FSX}
Your control settings = Standard.xml {C:\Users\User Name\AppData\Roaming\Microsoft\FSX\Controls}
Logbook.BIN and flight plan files {C:\Users\User Name\Documents\Flight Simulator X Files}
scenery.cfg {C:\ProgramData\Microsoft\FSX}