I know there are several related entries regarding NU14 but I am enraged that NU15 has apparently the same problem when using Registry compress - it will kill your system for sure!!
I am using an HP system executing System/7-prof. After running Registry compress my system crashed with "blue screen" (flashed for 0.5 seconds). A system restore was not possible because "you must enable System Protection on this drive" is the status. This status cannot be changed, sfc /scannow will fail with "system repair pending - reboot".
I spent two+ hours with HP support; the best they could offer was reinstall system. I spent another half day searching on the internet but found no remedy. I was furious about Norton to sell such a piece of junk.
However, I didn't give up. Finally I encountered an entry on the web reporting that the registry may have been corrupted which made lots of sense based on the operation I performed. I managed after many failed tries with the horrible HP-recovery software to get to a command prompt and found that the current registries were a fraction(size) of the prior ones (*.rmbak). I renamed the originals to *.old and renamed to *.rmbak to current = voilĂ , the system booted. In the course of this recovery I lost a full Sunday and I'll complain bitterly to Norton.
P.S. If you work with the HP recovery software, you need to make the changed on D: (C: is empty)