The Snow Leopard upgrade only works if you're already running Leopard. It's the equivalent of a Service Pack on Windows (which are, incidentally, free).
Windows 7 can be installed on any machine you like, no previous versions required.
While Snow Leopard is maybe not as big as most other updates to the Mac OS, please don't equate OSX versions with Service Packs on Windows. They're not just small updates, they're entire overhauls of large parts of the OS. For instance, Snow Leopard includes an entire re-write of the Finder.
I could also argue that Windows XP was a "minor upgrade" from Win2k, because Win2k is WindowsNT 5.0 and XP is 5.1. In a similar manner, Vista is NT6 and Windows 7 is NT6.1.
The numbers don't really have anything to do with anything.
It was the closest thing I could think of - not trying to undermine the work in/value of Snow Leopard (I don't know enough about it to make that judgement call). Apologies if that's how it sounded.
(Esp. as one could call Windows 7 the much needed service pack to Vista! ;) )
No worries. I'm a lifelong Mac guy, and with the 10.x naming scheme they've chosen for OSX, there are a lot of trolls that basically say "o lol it's just 10.3 to 10.4, it's like XP to XPSP2!!!!111". So you just pulled out my gut-check reaction, sorry about that.
