How do i add an OBDC connection?

I have attached the .mdf and .ldf files to a new database in Microsoft SQL Server Manager Express studio using the sp_attach_db command. The database seems to have been created using the old files from another server without any problem. When i try to create an OBDC connection to the database i recieve the error:

Connection Failed:
SQL state: '01000'
SQL server error: 53
[microsoft][ODBC SQL server driver][DBNETLIB]Connection Open
(connect()).
Connection Failed:
SQL state: '08001'
SQL Server Error: 17
[Microsoft][ODBC SQL Server Driver][ODBCNETLIB] SQL Server does not exists or access is denied

This is the first sql database i have tried to create, could i have missed a step?