Upgrade Mac OS X v 10.4.11 to v 10.5

No.

10.5 is Leopard and you have to buy it.

How can we upgrade to 10.5 when Apple don't even sell the disc anymore?

Come on Apple get your act together, if you stop selling new versions of OS X that support PowerPC then at least you should still sell the last version that did. My Mac Mini is still used to store my music collection and stills works, so let us upgrade to 10.5 to give the machine a little more life. If Microsoft can still support XP then you should at least support users to upgrade to 10.5.

Mike

Apple probably didn't realize that some users would wait until Leopard was itself superceded by Snow Leopard before buying it.

Car manufacturers have the same annoying habit of not selling brand new five-year old models as well.

You can still get Leopard from Apple if you call them and ask for a Product Specialist.

Or you may be able to buy it on Amazon or eBay. make sure you are offered an actual Leopard System retail disk, and not an upgrade or machine specific install disk.