Though a clean installation is always the safest route, it is not necessary. Just run the uninstaller for the old version and install the new one. Be sure to keep your user settings, but do not open them in V5, create a new user in V5 and import your settings (a new feature). Metasync, EDL manager etc all have installers that will automatically delete the old versions. You will love V5!
Dave
db Editorial
Avid Systems in Dallas, TX