I keep hitting this problem when I try to debug my Windows 8 apps and there is a copy already installed on another user account:
DEP0700 : Registratio
This is similar to some other answers, especially @Pavel Nazarov's, but works for different users. And it's different from the accepted answer because you don't need to install any programs.
In Windows Powershell in admin mode, run:
get-appxpackage -all | where name -eq "{{ App Name }}" | remove-appxpackage