Scenario: You install HomeSite 4.5 or Studio 4.5 and receive the error message "previous version not found," and are not able to continue.
What's the Problem? The HomeSite 4.5 upgrade will not work if there is any instance of HomeSite 4.5 on your system. For example, If you previously had HomeSite 4.5 Evaluation or Beta version on your system.
Solutions to the problem available in the article at http://www.allaire.com/Handlers/index.cfm?ID=13935.