The method is simple enough that I feel stupid not to know this. All you have to do is attach the .mdf file to the SQL Server. How? Open the SQL Server Enterprise Manager, open the tree (Console Root > Microsoft SQL Servers > SQL Server Group > (Your SQL Server) > Database) right-click on the database and select All Tasks > Attach Database. And then, just select the .mdf file, click OK and you are done. The process is almost instantaneous. So for 50 databases you could finish it less than 2 minutes.

If you're not sure what I'm talking about, you could always start with the default database ship with SQL Server. Right cilck on the Northwind database and select All Task > Detach Database
. After that follow the step above.
