OK, I've been running 5 for some time and decided to remove version 4 to clear out some space. When I did this, it stripped all my cameras off as well as my version 5 registration number, which I can't find. What do I do now to get 5 back up and running?

Did you export settings, or do you have backups ? If not you will need to email Support.

thanks. I'll contact support.