Mark, you're partially right

Helvetica is a font that has long been automatically included in the Mac OS, but it's not strictly a Mac font. There are PC versions.
Randy, you don't need ATM to install a font; ATM is used to smooth out screen displays. Whether you need it or not depends on your OS. If you have Arial, that may be all you need unless you specifically must have Helvetica for a project. Arial was developed by Microsoft as a derivative of Helvetica. And no, it's not a free font; if you need it do a search at [url=http://www.myfonts.com/]MyFonts.[/url[