I think you're going to be stuck with a reinstall. I've never seen anything that indicates that you can convert a named instance of SQL Server to a default instance. Plus this FAQ (http://support.microsoft.com/default.aspx?scid=kb;en-us;260414) indicates that you can't even change the instance name without reinstalling.

-Mike

>We just installed SQL server 2000 and got it up and running on a limited basis. We have now run into a snag. It appears that when this was installed while there is only one instance of SQL it is named. When we tried to upgrade an e-mail filtering program it could not communicate with SQL (even though it found it) because it was named and not listed as the default instance. (don't ask me why that was THEIR company line) My question is can I remove the named portion (or alter it some way) to be viewed as the default instance? I will try most things short of reinstalling SQL server, which is what they wanted me to do!!!!
>
>Thanks in advance
>Kelly