Windows Service with WCF not starting, Private Key Error

So I'm on a new computer now, and getting this "The certificate 'CN=test" must have a private key that is capable of key exchange. The process must have access rights for the private key." error again.

I want the Service to have access to the key, etc, and used winhttpcertcfg to assign permissions to the current user, but it says already assigned, but what "User" does a Windows Service run under? I tried using cacls.exe but got "The file replication service API was called incorrectly".

Am I able to create a certificate with a private key embedded and give access to any local Windows Service so that I don't have to worry about all this private key stuff? I have a client desktop app which interacts with a WCF service (inside Windows Service) which is installed locally or remotely (access by TCP) and the service then accesses a backend database.