There will be a button on the back of the casio or there will be a link on the board that forces a low level factory restore of the calculator, that is above and beyond software.
How much of a reset that performs, is gods best guess, there is always the chance the firmware won't reload.
Your two options 1 you will need to get seen by a casio engineer team, or 2 diy by ref to manuals and chip infos, if your expert enough to know how to short a data reset on the chip with a pull down resistor link.
The info about the chip can be found on the thread,
http://www.casiocalc...?showtopic=4671Read through the data sheets before going any further, if you don't see what you need to do, or don't know what your doing, refer to the casio people to restore it to norm, if you messed with the functions, they will probably charge you a fee for reflashing the firmware restore.
Basically those are your options, DIY from the guides, or shell out to pay the fellow that does it for a living.
I am sorry you have got into a state of needing to reconfigure your options, really the cheaper option is to buy the calculator that does what you need.
Casio are really helpful people, I can't see why anyone wants to short change the company just for the sake of it, sure if you need to mod a function somehow, its great to know how to do it, but 16 squids for an fx991ES its nothing compared to the cost of engineering time if you break it, and need it fixed. I would look seriously at the programming infos on the chip, and how to do a complete restore, if you are going to mod the Calc in any way, at least go by the book the guys that made it wrote for you!
When you understand what you have actually got for 16 pounds, you will wonder just why on earth you even thought about messing about?
My history with casio started with a fx451 with a membrane, I moved to a fx570B in the late 80's and these were with me for 20 odd years. I bought a 991ES a while back, and another one recently as a safety backup just in case some blighter nicks it from me when I am old and grey.
Casio are such a good company, look at all the helpful support sites online that are aimed to help you! All that they offer for what 16 quid and a call to register?
DONT TAKE ALL THAT or CASIO, FOR GRANTED, JUST THINK FOR FIVE MINUTES, WHERE WOULD YOU BE IN THE WORLD, WITHOUT THEM, OR WITHOUT A CALCULATOR AT ALL? IF JAPAN JUST WOKE UP TOMMORROW AND SAID, WERE ON HOLIDAY?
ANY GOOD AT LOGS? GOT A TRIG TABLE? KNOW HOW TO USE A SLIDE RULE? ANY GOOD WITH THE ABACUS? RIGHT, I remember the basics, and life is so easy with a calculator, and I KNOW FOR SURE THERE ARE THOUSANDS OF KIDS OUT THERE, WHO ARE NOT BEING TAUGHT AND HAVE NOT BEEN TAUGHT, what to do, or how to do things when the calculator is not there!
I must ask this, why the devil did you risk breaking it in the first place? THINK HARD BEFORE YOU TRY TO MOD YOUR CALCULATOR, ONCE YOU GET IT BACK TO THE BEGINNING.
