Vista Home Premium 32 bit OEM Anytime Upgrade to 64 bit

Ok,

I've been researching this and have found alot of convoluted answers but
none that really answers the question.

I have an OEM Vista Home Premium DVD. The disk says it includes anytime
upgrade but it also says it only contains 32 bit software. If I want to
upgrade (By upgrade I mean clean install to 64 bit but using anytime upgrade
to do it) do I need to purchase the 64 bit anytime upgrade disk which
microsft provides for the cost of shipping or can it be done from my current
installation disk. The anytime upgrade disk purchase site says: "Windows
Anytime Upgrade discs are available in 32 and 64-bit.
Note: Your upgrade disc must match the current system type of the computer
you want to upgrade. 32-bit upgrades are only valid for 32-bit systems and
64-bit upgrades are only valid for 64-bit systems. "
But if you want to "Anytime Upgrade" to 64 bit from 32 bit and your OEM disk
says it only has 32 bit software on it, do you need to purchase this 64 bit
upgrade disk ... or is it not even possible to "Anytime Upgrade" OEM 32 bit
Software to 64 bit and does it require the purchase of the full upgrade
software. Everything I've read about "Anytime Upgrade" makes it seem that it
should be possible (with a clean install) but its the fact that my
installation disk says it only has 32 bit software on it that is confusing
me. I've also read that all installation disks are the same and contain all
the versions of windows 64 and 32 but if this is true why does my disk say it
only has the 32 bit software on it.

Thanks