Exchange Info. Store service disabled

I’m running exchange 2000 on my Win2k server (sp4).My problem is i am not sending/receiving anything due to the fact that the Microsoft Exchange Information Store service has somehow changed it’s startup value from ‘manual’ to ‘disabled’, & the service status reads as ‘stopped’& all the available options (start,stop,pause & resume)have all been greyed out, therefore not allowing me to select to restart the service. I have rebooted the server, but still the same problems exist……….. Any ideas????