right click on the pst, and go to properties. i don't have 2k installed on my pc, and i'm too lazy to walk down the flight of stairs to my other pc that does, but there should be a tab that says security. click it, then click add. type Administrator, or whatever the name of the admin account is, hit ok, put a checkmark in full control, hit ok again, then import away
that's assuming the drive is NTFS, if it's not, then i have no clue, because the error you are getting is yes, because the ntfs perms set on that file are only for the previous admin user, not the current ones on this install