Bios Update-Upgrading Windows XP 32-bit to Windows 7 64-bit

I'm currently running Windows XP Professional 32-bit. I have a preorder set for Windows 7 Professional 64-bit. I understand that I will need to do a clean install, which isn't a problem. However, I have one problem. Since this is a student offer I am taking advantage of, Microsoft are limiting me to an upgrade edition of either 32-bit or 64-bit to download. Whilst I have read that the upgrade editions can be used to clean install so long as a prior version of Windows is detected, I am unsure as to whether it will work due to the preordered install being a 64-bit.

Will I be able to start this 64-bit install of Windows 7 Professional from within my 32-bit Windows XP Professional? If not, will I be able to create a USB boot key and install it from within the BIOS? I know this is possible with the full edition, but don't forget this is the upgrade edition I have ordered (and sadly the only version I can order), so will the upgrade edition be able to detect my Windows XP installation from within the BIOS? I have also ordered the Windows 7 Disk Kit alongside the digital download if that helps?