You sould reinstall the operating system.
Use the link below to install TIConnect softwarehttp://education.ti.com/educationportal/sites/US/productDetail/us_ti_connect.html
You can also download the latest OS there.
Install TI connect on your computer and run it to open the main Window. Then connect
you calculator to a USB port and, in the TIConnect main window Click
the TIDeviceInfo icon. Software will try to retrieve the info. If it
does your calculator is fine.
If it tells you Device Not found ,
Click communication settings in same pop up window where it said Not
found, and Select Device, Select Cable, Select Port and Click OK..
you are lucky and it works, you should reinstall the OS, which can be
downloaded from education.ti.com. You drag and drop the OS on the
TIconnect main window. Calculator must of couse be connected to computer.
you have problem with TIconnect, use the calc-to-calc cable to transfer
the OS of a working calculator. Yous should be on Receive mode
[2nd][Link] --->>Receive. (When both calculators are ready hit
enter.) The other calculator, you guessed exactly right, must be on
Send [2nd][Link][SEND][G:SendOS]. (When both calculators hit [ENTER])
all that does not work, then it may be time to head for a place of
worship to pray for its resurection, or look for a repair shop.
Hope it helps