Ok, so I stand corrected. I opened up PPT, clicked off the collapse windows option, then opened PPT again, but when I opened it again I actually used a start-menu option that linked to a separate instance of office on the same machine - so I effectively had 2 different PPTs running (this was instead of using the desktop shortcut I usually use but couldn't be bothered looking for). So I guess that is not that different from the work-around you posted - opening PPT under another user or opening a completely separate instance will give you the same result (but I wouldn't suggest having 2 versions of Office on one machine, it does stuff things up a lot).

But you're right, a single instance won't give you two windows in 2007.