Either use a password, or in the case of a media folder with no important information in it (music and movies only, that you want to access with a TV or Apple TV or something), give read and execute permissions to the "everyone" group.
Honestly though, you should set up your home group on one, and join that home group with the other and permissions should be set automatically. You can't create a homegroup on a basic Windows 7 install though; you can only create one in Windows 7 Home Premium, Professional, Ultimate, or Enterprise editions.