Apple is preparing to issue Mac OS X Lion upgrade in the coming month, July. The update was announced on OCT 2010 and since then developers were allowed to download beta versions. I’ve downloaded Mac OS X Lion 10.7 preview 3 as a DMG file and upgraded my existing Snow Leopard installation with it. While announcing iOS 5 Apple CEO mentioned that they will list Lion to the Mac app store, instead of providing DVD disc for backup. Therefore, to do a new OS X Lion installation, we first need to install the Snow Leopard and then upgrade to Lion from the app store.