Have you found the keys that now has the DOC, EE and ENTER functions? It might be worth trying the combination of these threes then hold them down while pressing ON and stuff. Else, you could try what is now HOME, ENTER and P, which was the original ClickPad version of the key combo to access this mode from what I can remember.

After a lot of trial and error, I finally got the right button combination and was able to format again. Any recommendations on which OS to install now?

I could use some serious help! I offered to update my friend's nspire CAS (touchpad model) to the new OS, because he was having trouble installing it. After some initial troubles, I managed to install the latest version of the OS by doing a complete formatting through the maintenance menu. However, upon turning on the calculator, nearly every button has been reassigned to a different function. After some messing around, I think I've determined that the calculator is stuck using the button mapping from the CAS clickpad model (the on/off button only works as such, and the doc button now acts as the home button). Because of this, I can no longer access the maintenance menu and install a different OS. Since the OS installed now is the latest version, I can't downgrade to a lower version through the nspire computer link software. I've tried various combinations to try to reach the maintenance menu, but I've had no luck.

Any suggestions? I'd hate to return the calculator with it being in worse shape than when I borrowed it.

EDIT: I'm now able to access the maintenance menu, but every reinstall of the OS results in the same button problem.