Mac App Store and multiple OS partitions I recently set up an additional Lion partition in addition to my existing partition for development reasons.

I was in the process of installing apps on this new volume through the Mac App Store, when I realized that it would not let me install apps that I had installed on the older partition.

For instance, when I was trying to install Twitter.app, since it exists on my older partition, the App Store lists it as "Installed". This prevents me from installing it on my new partition. 

Is there a hidden preference that would limit the App Store to only search the boot volume for installed apps? Is there a better way to manage installations across multiple volumes using the App Store?
At present the app isn't set up to restrict its spotlight search to any specific volume. That behavior falls as a natural consequence of "the Mac way"  of letting an app reside anywhere and still run. 

You can use disk utility to unmount that volume when it's time to install or update as a workaround.