Winamp 5.8 has the clear all feature for MRUs as does 5.666 and 5.58 versions. But that's not what the user asked for.
Open your start menu and type "run" then strike the enter key.
In the "Run" box type in or copy/paste in the following line:
PHP Code:
explorer /select,"%APPDATA%\Winamp\winamp.ini"
It should open a new file explorer with the correct file to edit already selected.
There CAN be more than 16 MRU entries and they don't necessarily have to be clustered together so you may have to find others, however, they should be restricted to the [Winamp] section in the INI file.