One iTunes Library Two Hard Drives

I want to share one iTunes Library or Media folder (Its the same thing isn't it?) between two bootable partitions. Each has its own copy of iTunes.

There are 3 partitions in total: The first 2 (mentioned above) each run an OS an the 3rd is a Data partition for storage. The Data partition is where I want to store my iTunes Media folder.I have managed to move and successfully run the iTunes Library/Media folder from the Data partition on the Lion partition. But it my computer won't play fair and share its musical toys with the other iTunes app.

I don't see any reason why this is not possible but just I can't get a shared parition to work on both Lion and Snow Leopard partitions. The partitions do have different versions of iTunes on if that makes a difference (Lion has iTunes 10 & SL has iTunes 11)?

I'd love to get this sorted iTunes takes up huge amount of space on my computer and I really miss my music when I'm working on Snow Leopard!

All helpful words an whispers much appreciated! 🙂