The process should still be the same. I believe that the MRS\App_Data\Config\AppConfig.xml file has been there since SmarterStats 3. Our customer service just didn't confirm that resolution against versions older than 6.x.
https://portal.smartertools.com/kb/a2472/reset-the-administrator-username-and-password.aspx
If you still can't find it, that's what our support department is good at helping with. Start a ticket and we'll walk you through it.
Grady Werner
SmarterTools Inc.
www.smartertools.com