NU is stuck in a loop.

Since scanning my registry with nu 16, I cannot consistently reboot my win 10 pc. without it jumping back into a norton u. scan of the h.d. that always fails at 44%. I have learned how to repair the master boot record which allows me to bypass the scan on rare occasion, and I have my pc back until the next time I reboot, and it reverts back to the nu scan which always fails    grrrrr.    wth   Can I save my system without completely doing a clean install of windows and loosing all my installed apps.???