You really need a full version to see Vista go on there since you don't have a direct upgrade option. When going to use a full version installation disk the Vista installer will archive any MS created folders in a "Windows.old" folder for retrieving files afterwards.
That's without any reformat and deletion of the current primary for seeing a clean install on a new primary. You should backup anything you haven't already in preparation for this. With a full install disk you simply boot from that to see the installer start up.