just open your new part file doc
edit your default settings-
ie: set as you wish to open
and then "Save as" prt template
hope this helps kelef
To do this you would create a new part/assembly/drawing, adjust the units under 'Document Properties', then go to 'File'> 'Save As', set the file type to part/assembly/drawing template, and overwrite the template.
Or you can go into 'File Locations', find all the folders for document templates, then go empty them of all templates. The next time you go to create a new file it should ask you to pick unit systems again.