I'm pretty sure that one of our SQL Server 2000 database instances has been corrupted for unknown reasons and that re-installation of SQL Server 2000 on the affected server is probably the only solution.
But just in case I don't actually have to go down that route (what a nightmare!), here are the errors I am getting:
Attempt to start SQLSERVERAGENT service from Admin Tools -> Services:
"Configuration Manager: A required entry in the registry is missing or an attempt to write to the registry failed" followed by "Insufficient system resources exist to complete the requested service"
Attempt to start MSSQLSERVER service from Admin Tools -> Services:
"Insufficient system resources exist to complete the requested service"
Attempt to start Database Services from SQL Server Service Manager:
"An error 3 - (The system cannot find the path specified) occurred while performing this service operation on the MSSQLServer service"
Doesn't look too good eh? The server is running Windows 2000 server - any suggestions would be much appreciated!