Purchased an "Open Box" calculator from eBay...
Original Calculator: Casio FX-9750GII
Original OS: 02.04.0701 (No Spreadsheet, No Natural Display, No Addins support, etc.)
New Calculator (Functionality-wise): Casio FX-9860GII
New OS: 02.05.0201
UPDATE PROCEDURES (This is what I did... Proceed at your own risk... YMMV)
Installed CASIO FA-124 Application (CESG502 driver is required), verified USB communication, then exited program
http://edu.casio.com/education/support_software/Found this utility to backup Original OS 2.04 (or 2.05)
http://www46.zippyshare.com/d/9f6bSkpF/779727/fxBackup.zipConnected USB cable to PC, pressed [F1] to start DataTrans and "Receiving. . ." was shown on display
Ran the program "fxBackup_204.exe" and pressed [Backup flash] and typed a backup filename
Backup process was successful, program was exited, and (RESTART) pressed on the back of the calculator
Found this utility (fxRemote v2.0.3.25) "fxRemote.zip" to restore backup OS flash images to calculator
https://tiplanet.org/modules/archives/download.php?id=4484Found this online discussion forum with loads of good references and links to information on this topic...
http://www.planet-casio.com/Fr/forums/topic9552-50-Transformer-Graph35+USB-en-Graph75.htmlConnected USB cable to PC then pressed [OPTN] + [EXP] + [AC / ON] + (RESTART) (on back of calculator using stylus)
Released (RESTART) first and then [OPTN] + [EXP] + [AC / ON] to show "OS ERROR" on the display (contrast was very dark).
Ran the program "fxRemote.exe" and checked the box labeled "Delete storage memory" to make sure storage area was properly cleared
Pressed [Recover flash] and selected filename "os_205_9860g3.fls" and clicked through some dialog boxes to continue process
Restore process was successful, exited program, pressed [F1] to initialize storage area, and finally pressed (RESTART)
SUCCESS!!!
Ran CASIO FA-124 to load some Addins which all work, along with all other functions including Natural Display which is now default
Some Related Resources:
Tutorial document that explains the underlying hardware similarities of Casio calculators (translate from French if needed)
http://tiplanet.org/forum/archives_voir.php?id=4489At first was unable to restore original OS backup, but then found this utility that helped fix the issue
https://tiplanet.org/forum/archives_voir.php?id=73834 
