Hi,
I've been testing MS Project 2007 on 6.2 and 7.0 beta. As Office 2007 doesn't work on 6.2, there was never much hope of getting Project 2007 to work there.
On 7.0 Beta, Project 2007 installs, and almost finishes starting up, but fails with an error saying that setup needs to be run again as it can't find the user configuration. I've not yet had time to try installing again on the final 7.0 release, but I'll be testing it in the near future. I don't think it's that far away from working with some tweaks.
I don't have access to earlier versions of Project, but these are more likely to work.
Paul