The Portable folder is used in MM4 as well for Portable installs. It has all the files that are normally in the User folder and Registry as the idea is that the install is Portable. As MM5 is only Portable for now it also uses this.

Was the Equalizer folder the last used folder by MM?

Went to find new image .. clicked on browse and explorer window opened to c:/program files(x86)/mediamonkey/equalizer

First this should have be c:/mediamonkey5/portable/artistimages

second why in a folder called portable?? Does this change if not a portable install?