Before you start setting up and configuring a database mirroring environment, it is always best to run through a simple checklist of basic requirements:
1. Verify that all server instances are at the same service pack level. In addition, the SQL Server edition you have must support database mirroring.
2. Verify that you have as much or more disk space available on the mirror server as on the principal server. You also need the same room for growth on both.
3. Verify that you have connectivity to each server from the others. You can most easily do this by trying to register each SQL Server instance in SSMS. If you can register the server, the server can be used for database mirroring. Do this for the principal, ...