Backup database failed, Operating system error 5(Access is denied.).

From Menu "Settings" -> "Application Setting" , click the button "Back database" to backup database to a folder.
SQL Server should have permission on a folder when database is backed up. By default, SQL Server  will backup in its root directory. But, this application allows us to save any folder.

So we need to set permission SQL Server user on the folder where you need to back up.

Here is the steps.
1. Right click the folder and click properties menu from the windows folder, where you want to take a backup
2. Un-check, "Read only - attribute"

3. Click the Security Tab and Click "Edit" button.
4. In the "Permission for .." folder Click the "Add" button.
5. From "Select Users and Groups" dialog enter  NT Service\MSSQL$SQLEXPRESS in the text box and click Check Names and then click Ok button as show below.

6.Next Select MSSQL Server in Users and Groups, Check the "Allow" Check box for Full Control and Modify .
Click on "Apply" button and Ok button.
and another ok button to close all dialog box.

This procedure is granting permission to SQL Server to write on other folders.