I always like having the latest system, and also (for security reasons) I always update everything. The thing is, theres a game I really want to make run. Its only supported on Lion. A year ago, when I upgraded to Mountain Lion, everything worked fine, even though it wasnt supported on ML. Now I cant make it work, probably because the installation itself is where the problem lies. Probably if I would install Lion, install the game, and then update the system, it would work. Maybe! But this is quite complicated and it doesnt guarantee the game properly working. (although it did before) So I was wondering something else can I install two versions of Mac OS X on my Mac? I was thinking of creating a partition just for the game, with Lion installed on it. That would be around 10 GB. What do you think? And how would I swap between both OSX?