I had SQL Server express edition installed on my development box and I had configured it to be a named instance. However after some time I felt I better use a default instance to save myself from some extra keystrokes. Though my connection string is in web.config and it is not a big deal to put few extra characters there, but I thought to convert the instance type of my DB server.
When I looked up in Google, it seems you can not change the named instance to default instance and vice versa. However I encountered one StackOverflow post which suggests few steps to make named instance behave as if it is default instance. You should use this workaround only when you are playing with a development box. You really should not try this on any of your critical database servers. Following is the link to the post: