This procedure worked for resetting the local W8 password on a laptop when the original was forgotten:
http://pcsupport.about.com/od/windows-8/a/reset-password-windows-8.htm
After creating a W8 boot flash drive with the media creator (minimum 4GB blank flash drive):
http://windows.microsoft.com/en-us/windows-8/create-reset-refresh-media
(The media creator will download the necessary W8 boot files, so no need for a DVD or ISO. It will download slowly, as apparently MS throttles it.)