I've noticed something that is equally amusing and worrying when one installs ML on the same disk as Lion, but on a separate partition. I've Lion on a partition called "Macintosh HD" and I've installed ML on another partition called "ML". Lion runs quite happily, but I see some odd behaviour in ML. Basically ML the will run the Applications, show services, report apps as installed in the app store that are actually on the Lion partition. For example, I have PathFinder installed on Lion and not ML. Yet, I can use PathFinder's "Show Info" service from ML by right clicking on a file. None of the applications installed on the Lion partition show up in ML's applications folder, but they will launch quite happily if I use a service or if I navigate to them directly via Lion's partition. I also can't install any of the apps from the App store, because they are reported as installed. I can bypass this by ejecting the Lion partition and then ML works as one would expect. The app store will now allow me to install apps. Thinking about it, it might be because I am using the same login name and password for both Lion and ML so I'll try that, but is there a way to prevent ML from accessing Lion's partition to look for Apps, services and so forth without dismounting the Lion partition?