If I buy a regular retail Snow Leopard disc (i.e. the £25 version), can I use it to upgrade a Mac from Tiger (10.4)?
This answer on the Apple Store’s Q&A site suggests it’ll work, but Apple seem to imply that you need the (significantly more expensive) Mac Box Set (“the Mac Box Set is the best way to upgrade your Mac experience, especially if you're still using Mac OS X Tiger.”).
Best Answer
Apple wants you to buy the Box Set in order to upgrade from Mac OS X Tiger 10.4 to Snow Leopard. Technically, you the Snow Leopard retail package will upgrade intel based Macs running Mac OS X Tiger 10.4, however it is against the terms of the End User License Agreement (EULA).
The Box Set includes additional software that typically comes with a new Mac (and some that doesn't) and it is recommended by Apple to 'upgrade your Mac experience' because it is more like buying a new Mac than just upgrading the operating system.
To hear it straight from Apple, here are the answers from Alan Eyzaguire, director of software product marketing at Apple Europe to this question.