If you have the classic version of Dark Age of Camelot and have not
installed Shrouded Isles you should use this installer. Otherwise you
should download the version specifically designed to upgrade Shrouded
Isles from here.

Dark Age of Camelot: Foundations is a free optional expansion to the
online role-playing game Dark Age of Camelot. With Foundations, Dark Age
of Camelot players and guilds can purchase, build, and decorate their
own personal houses, choosing from a variety of styles and hundreds of
exterior and interior objects. For more information visit
www.camelotherald.com/housing/