Upgrade Version On Clean Partition?

An anonymous user sent me the following message: (3/4/2007)i purchased vista the other day and did exactly what you did by formatting my drives, and now it tells me that my product key is for upgrades only, can you please send me an e-mail and tell me how you went about fixing your issue. my e-mail address is @hotmail.com. I thought this may be of more use in the forum than a private reply, so here goes.

First up - this is a dumb way to do stuff. I only did it because I thought Vista would install as XP did (i.e. I'd just need to drop my XP CD in the drive during the installation. I was wrong. Vista upgrades can only be done from inside a previous OS.). I used the XP CD to reformat all of my partitions. I then put XP onto a partition I later planned to use for my page file. I did a default install of XP until I could boot into it, and then (without activating it) dropped the Vista DVD into the drive. I used my keycode there (an upgrade one), and it accepted it. I then directed it to install Vista on the primary partition, so I had a clean install.

Cue several reboots. I then had a clean copy of Vista, and an old copy of XP, which I could reach via a dualboot menu shown at boot time. This was no good to me, I have no use for XP, so I rebooted from the XP CD, and reformatted the partition with XP on. This removed the dual boot screen, and by a bit of BIOS jiggery pokery to make my boot devices order floppy, DVD, Vista partition I was all sorted. I waited a few days before activating just to make sure it was stable, and it has been so far!