Yes you can buy the Premium upgrade but you will need to send off for or
otherwise obtain the x64 media since it won't be in the box. There isn't
separate x86 and x64 versions except for the OEM packages.

"mrudis" <mrudis@discussions.microsoft.com> wrote in message
news:0C9BE17D-C9C1-4D1B-A0B5-E8BA23C78A12@microsoft.com...
>I am currently running the 32-bit version of XP Pro and I want to "upgrade"
> to the 64-bit Vista Home Premium (I have a the Intel EE6600 dual core, so
> I
> can handle 64-bit). I understand that I have to do a clean install, but
> I'm
> confused if I can buy the Vista Home Premium Upgrade (since I do have a
> active copy of XP Pro) or do I have to pay double for the Standard (Full)
> version.
>
> Also, is there a seperate box for 32-bit versus 64-bit Vista Home Premium
> (I
> see different ones available for OEM, but not for the retail box).
>
> Thanks in advance for your help