I'm up to the latest Sonar Professional on a dual core 2.0GHZ laptop with a maximum 3GB of ram and Windows 7! It's beginning to feel the stress of my virtual instrument collection! I keep all my Sonar versions for the same reason, you never know what computer is going to up to the job! I have cakewalk Pro 8 (before that it was cakewalk Dos), Sonar Home Studio 6, Studio 7, 8, 8.5, X2,X3 and now Sonar Professional! If cakewalk streamlines it's code a bit, much like Steingberg does with it's current version of cubase, we won't have to switch up versions at all!