Well, I can see that it should be nice 'n easy, however the 64-bit install apparently wants to barf all over my hardware configuration for some reason, which has had rather annoying ramifications.
So, I go to run the setup and each time it gets to the end of the intitial "copying files" part the install decides to BSOD on me. This lead me to spend the night a.) trying to find and create some DOS boot device to upgrade the BIOS of the 955X motherboard (I managed to figure out out to make a USB Floppy drive detect and boot in the end - so I learned something new and thats certainly easier than plugging an internal floppy drive back in), and then b.) toggling most of the BIOS settings to see what the install isn't liking.
Seemingly it appeared that the install doesn't like my drive setup - changing the southbrigde SATA support from "Enchanced IDE" mode appeared to make some difference. Finally, the setup now gets into the the actual seup element. So, I type on my locale settings, then the licence key and its all happy and goes to the drive setup area. Here, I want to repartition my drives, which means formatting over the old Windows install - all done OK, drives partitioned as wanted, formatted and the Vista install carries on. It says that its doing the actual file copy so I go downstairs and hack some Marvel baddies on the XBOX while it runs. So, I go to check on it later and, sure enough, BSOD.
Now I go to install again, and it gets to the drive selection, however this time the "Next" button is greyed. Oh, joy. Its an upgrade license (even though its a Vista Ultimate upgrade) and because I reparitioned and formatted the drives from the previous setup attempt it can't see a valid XP license in order for it to Install!
So, now I have to go back, install XP (and probably phone up to get that validated) and then go back and try the Vista install again in the hope that the 64-bit install may actually decide to work!