The option to upgrade or reinstall the OS on these calculators is hidden deep within the UI nightmare known as TI Connect.
- Make sure you have TI Connect installed.
- Connect calculator to PC, make sure it shows in TI Connect
- Select TI DeviceExplorer
- From the menu at the top, select Tools > TI OS Downloader
- The wizard will guide you through the installation process. It has an automated downloader built in so you do not have to worry about downloading the correct OS version from the TI website.