Is there 1 default instance per OS Server or per SQL Server?

On a Server 2k3 x64, I've installed SQL Server 2000 x32 SP4 and SQL Server 2005 x64. When installing both SQL Server 2000 and 2005 on the same server, does each SQL Server have it's own "default instance" or there can only be one "default instance" per server? TIA, Gary.

There can only be one default instance per OS.

Be carefull when installing SQL 2005 on a SQL 2000 machine. It's very easy to upgrade the existing instance without releasing it.

|||Well that explains what happened. I noticed SQL Server 2005 was showing SQL Server 2000 databases. The good thing is it only the test server, not production. But since SQL Server 2000 instance has been updated, I'm assuming I'll have to uninstall both SQL Server 2000 and 2005 in order to set both up correctly? Is there a shortcut to fix this?|||

Correct, there is no way to revert to DB's back to SQL 2000. The default instance naming is the same in both products to make upgrade easier. You can always supply a different instance name with the second install to run both editions side by side.

Thanks,
Sam Lester (MSFT)

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