Working with Adobe Media Server (used to be called Flash Media Server), I had a situation in which I couldn't seem to remember my admin password.
This turned out to be a pretty simple fix. If you go to where your Adobe Media Server is installed you will find a program called AMSAdmin.exe (or fmsadmin.exe). By entering in this command, you will be able to type in your new password.
$ amsadmin -console -u username