The White Circle as the Status of a SQL Server Instance and SQL Server Agent (Agent XPs disabled)

I try to create a job in SQL Server 2008, but notice the following:

Problem 1: 
The SQL Server service has started and it works, but why the icon is a white circle, instead of the green circle with a white arrow inside?

Solution:

The white circle indicates the instance is in an intermediate status. The possible reason for the white circle is that I have other versions of SQL Server services running on the same machine. When I disconnect all of the other running instances, and restart SQL Server 2008, it works as desired with the green circle.

Problem 2: 
For the SQL Server Agent, I see the SQL Server Agent is disabled. I cannot start, stop, or restart the agent service from SSMS. All option are grey. The SQL Server Configuration Manager also shows it is off.

Solution:
After I start the agent service, it works normally. If the issue is more complicated, this article may be helpful for trouble-shooting.