My problem is totally opposite with this member. For my case, I cannot login to mssql 2008 without specify the instance name. I am thinking how to connect to mssql by just having the server name. This is because the application I used does not allow symbol like (MSSQL\MYDB). Please further asking if I am not giving enough information.
Solved: By setting server roles "sysadmin", then the problem is being solved. Documentation of the application mentioned that as long as fill in the server name and also port number, the installation can automatically resolves the instance name from provided port. Appreciate for any reply.