Don't expect to upgrade from XP(32) to Vista (64)
Can I upgrade from a 32-bit version of Windows to a 64-bit version of Windows?
No. If you are currently running a 32-bit version of Windows, you can only upgrade to another 32-bit version of Windows. Similarly, if you are running a 64-bit version of Windows, you can only upgrade to another 64-bit version of Windows.
