Eraser app - Edit - Preferences - Erasing - Answer "no" to upgrading the format, if asked.
Side note: answering "yes" seems to corrupt the settings but that is out of the scope of this post. I don't think that is a portable bug.
If you create a new erasing method, Eraser creates the file %windir%\Eraser.INI. Can Eraser portable be updated to redirect this file? Thanks!
(FYI, an all zeroes one pass erasing method is useful for compacting virtual hard disks.)