You cannot use a Vista retail upgrade edition unless you have a qualifying
legacy Windows running on your computer. If you cannot find the XP Home cd
and product key to reinstall Home with then you will need to purchase a full
edition of Vista. Is there any possibility that you made an image backup of
your XP Home volume before you installed Vista RC1?

"the_retro_fox" <theretrofox@discussions.microsoft.com> wrote in message
news:6BC38836-C35A-4056-8F74-F72A5AD9EFB6@microsoft.com...
> Hi all- I had a question
>
> I did a clean install of Windows Vista RC1 over my copy of windows xp home
> edition. I then later realized that I had lost my XP install disk and
> serial
> number. Does this mean i will be unelegible for the upgrade edition of
> Windows Vista Home Premium? Will i have to pay the 259.00 for the full
> version or can i pay 159.00 for the upgrade version?