BugNET

I was wondering where is the database for the BugNET BN. I understood that the Bugnet database created on my SQLEXPRESS instance is completely empty. I tried to rename this empty database to see the side effects. The BN continued to work properly until the first widows restart. Then I understood that this database is essential allthough it is empty! After some search, I found the Bugnet.mdf, Bugnet.ldf, database.mdf, database.ldf into the App_Data folder. I tried to copy theese four files for my backup but I couldn't getting the message "It is beeing used by another person or program". I stopped SQL Server express instance but unfortunatelly the error message was the same. I tried to attach the mdf files from the Management Studio but it couldn't be done successfully. I found into the task manager that ASPNET user is running an SQL server process. I killed that process and then I got my copy-paste-zip-backup. In the end, I restarted my machine because I couldn't find how to restart that SQL server process for the ASPNET user.

My Questions:

Is there an easy way to backup my BN database?

Why BN continous to work when I stop the SQLSEVER EXPRESS instance but fails after the restart?

How can clarify the way that BN connects to the database?