You are not able to install Parallels Desktop. The following error message appears:
Parallels Desktop cannot be installed because there is a non-root user account with the UID 0 in your system. Problem ID: 15476"
This issue may be caused by Mac OS X misconfiguration: if the OS X has several user accounts with the same UIDs, particularly with UID=0. This ID should belong to root user account only. For more information please visit https://en.wikipedia.org/wiki/Superuser
To check the user accounts' UIDs please execute the following command in Terminal (Finder > Applications > Utilities > Terminal):
dscl . -list /Users UniqueID
The output supposed to show you the list of all users (system as well) with their IDs.
If you find any user account with UID=0 (except of root) - this is the root cause of the issue with Parallels Desktop.
NOTE: Please do not change user UIDs on your own. Contact Apple Support for further assistance.
After non-root users' UIDs are fixed, please try to install Parallels Desktop again.