SQL Server Agent

I am running 3 instances of SQL2000 SP3a on a windows 2000 server. Over the weekend, the server was restarted due to security patches being applied. All 3 instances are setup the same (Automatically start SQL Server Agent when restarting server). The 2 named instances started the agent fine but the default instance did not. There are no errors in the log. When I started it manually this morning, it started fine with no errors. Does anyone have any idea why the agent would not have started automatically?

Thanks,
Ken

Check the dependency of SQL Agent service in Control Panel - Services to make sure MSSQLServer is listed as dependent service.