As has been stated many times on the newsgroup, you will have to use
telephone activation and hang on to talk to an operator and explain your
situation. Assuming you have uninstalled the 32-bit version you will be
able to get activated.

"VistaHeadache" <VistaHeadache@discussions.microsoft.com> wrote in message
news:729487DB-64AE-4DDC-BA34-29BB413A39A3@microsoft.com...
> Ok, I wanted to start using 64bit Vista Home Premium. I bought and have
> the
> 32bit version. I ordered a 64bit version from Microsoft's website. I
> installed the 64bit version, using my same key. When I go to activate it,
> it
> says it's already in use? I seriously hope they don't expect me to buy
> another key just because I went to 64bit...any help would be appreciated.