Google Earth can be downloaded by itself, without having to dl Google Pack. I personally don't like Google Pack because parts of it were things I didn't need, parts were things I already had, and Google Desktop slowed my pc down too much.
When you download Google Earth, it does tell you in the agreement that it uses the Google Updater, and lets you know that the updater is also included in Google Pack.
TERMS & CONDITIONS
Welcome to Google! This software will be installed using the Google Updater, which is included in the Google Pack.
When I recently downloaded the updated version of Google Earth, it installed Google Earth and the updater and nothing else.
Google Earth's homepage
http://earth.google.com/
As far as I know, you can also pick and choose which applications of Google Pack you want to download and install, if you elect to download google pack.