Do the commands on the Flamingo nxt 5.0 menu still run?
If they are unknown commands, you just need to close the toolbar file.
If the commands still run, delete flamingo folders from these locations.
%APPDATA%\McNeel\Rhinoceros\5.0\Plug-ins (The toolar file is stored here by default.)
C:\Program Files\Common Files\McNeel\Rhinoceros\5.0\Plug-ins