System Error: go to maintenance menu (see below)

Maintenance Menu: Press and hold "doc"+"enter"+"EE"
4. Complete format (includes operating system)
Download computer Link Software from education.ti.com (and install)
Download OS for your device
Open Link Software and under "Extras" Install OS (BS in German)
Done!

To Charge even when formated or in system error:
T enter Diagnostic Menu: Press and hold "esc" + "menu" + ""
to charge use:number 5. Manual Test, ("enter"+"on"+"enter")
then you will be in the "Battery Pack Charging" Option