MSDE Problem - SQL Server not found or access denied

I am running the MSDE 2000 Setup off the SQL Server 2000 Developer Edition CD.

After installation is complete, there is a service under the Control Panel -> Services window
called MSSQL$GregInstance. I then start that service.

But now when I try to connect to the database using

osql -E -S GregInstance

I get told that the SQL Server does not exist or access denied. Even though the server is running. I have also tried

osql -E -S localhost

but no luck. Why can it not find the instance of SQL Server?

Note : SQL Server 2000 is not installed on the machine, only this MSDE instance.

Thanks
GregNot to worry, I forgot to add in the name of the pc with a \ before the instance name...

i.e

osql -E -S GREG\GregInstance