Thanks to Paul Fauth for sending me this info from the MSDN subscriber´s website:

Where are Office XP and Whistler Beta 2?

Each installation of Office XP and Whistler Beta 2 must be activated with a unique Product Key that will be printed on a sticker on the installation disc. Because the products cannot be installed without this key, they will not be available on MSDN Subscriber Downloads until after the subscription shipments commence.