I upgraded MsSQL database version from MsSQL Server 2008 Express Edition to MsSQL Server 2008 Enterprise Edition. After upgrade operation, Agent XPs was disabled and MsSQL Server Agent servis could not start. I reconfigured Agent XPs configuration. The problem resolved.
Management Studio Object Explorer does not display the contents of the SQL Server Agent node unless these extended stored procedures are enabled regardless of the SQL Server Agent service state.
Agent XPs Possible Values
0, indicating that SQL Server Agent extended stored procedures are not available (the default).
1, indicating that SQL Server Agent extended stored procedures are available.
Show Current Value
EXEC SP_CONFIGURE ‘Agent XPs’
Reconfigure Agent XPs
EXEC SP_CONFIGURE ‘show advanced options’, 1;
GO
RECONFIGURE;
GO
SP_CONFIGURE ‘Agent XPs’, 1;
GO
RECONFIGURE
GO
After these parameter change operations you can restart agent service or sql server service to show Agent XPs enabled.
After all operations, If agent service does not start, you can try that Agent service on services.msc user change to local. That can resolve problem.
Source : Microsoft Offical Documents