Customize Windows Explorer Popup Details

When I hover my mouse pointer over an mp3 file, it pops up a tooltip containing Type, Size, Artist, and Length. I wish to add Bitrate (and maybe a few other descriptors). I've tried a 3rd party tool which didn't work, and none of the registry hack screenshots look like my registry screen. Can anyone point me to what should be a simple fix? Thanks.

I found what I needed here" A Somewhat Integrated Life: Customizing Windows 7 Explorer Infotip

The trick was to edit the .mp3 entry in HKEY_CLASSES_ROOT\SystemFileAssociations\.mp3, not HKEY_CLASSES_ROOT\.mp3.

I hope this helps anyone else needing to customize the Tooltip popup.