a) delete the various old "OpenVPMS Release x.y now available" post from the front page
b) edit http://www.openvpms.org/download to add a section at the bottom (with an #earlierversions anchor) giving the download links for earlier versions
c) edit the front page current 1.7.1 post to add "If you need an earlier version, click here" with here jumping to the http://www.openvpms.org/download#earlierversions