To uninstall PIX4Dmapper software: 

1. In the Windows Search, type Add or remove programs.
2. Scroll to find PIX4Dmapper and click the application.
3. Click Uninstall.
4. On the path where PIX4Dmapper was installed (default is C:\Program Files\Pix4Dmapper), ensure this folder does not exist anymore. If it exists, DELETE this Pix4Dmapper folder.
5. In C:\Users\Your Username\AppData\Local\pix4d, ensure the folder Pix4Dmapper does not exist anymore. If it exists, DELETE this Pix4Dmapper folder.
6.  In the Windows Search type regedit and search for the folder stored in the path: HKEY_CURRENT_USER\Software\pix4d\pix4dmapper and ensure this folder does not exist anymore. If it exists, DELETE this PIX4Dmapper folder.
7. Restart the computer.
8. Reinstall the latest stable version of the software: https://www.pix4d.com/download/pix4dmapper/