With regard to dells, some dells have a recovery partition and no OS media. Installing/upgrading the OS will destroy it. However you are able to make or send off for a CD.
No ,it would have 2 partitions,Vista + the recovery ,you could format the 1st partition and make 2 partions in it, ending up with two partition + the recovery partition.load xp on the first partition and the recovery of vista on the second partition .
Guy i know bought a new Dell with vista ,he hated it ,most of his software didn't work with vista,so he wanted to buy xp pro ,remove vista and install xp ,Dell told him it would void his warranty