1. Pull out a battery
2. Wait at least 5 seconds
3. Hold DEL
4. Put the battery back in
A screen should popup when you insert the battery. After fiddling through the two screens, your calculator might be fixed.
If not:
5. Repeat the first 4 steps, and after your calculator turns off after the scary messages, hold CLEAR and press the ON button
If you calculator works now, you will have to clear all memory in the memory management screen.
If not:
6. Repeat the first 4 steps, but have you calculator connected to your computer with your computer ready to send the new OS through ti-connect
7. When the calculator says send, send the OS
If you calculator is not fixed at this point, try step 5 again.
If none of that works, then you're probably doing something wrong