After uninstall the Microsoft SQL Server and reinstall a fresh SQL Server, Try to append, i just cannot connect to the previous database created. However, the old database still remain in the MSSQL, Data folder.
You need to attach back the database to SQL server. If you reinstall MSSQL, the server will not automatically bring your database online until you attach it back to the server.
Connect your server with MS SQL management studio. Right click on the databases node, and select Attach.