Upgrading (clean install) from XP to Windows 7 in Bootcamp

I have a MAC PRO with a quad-core intel processor, 8GB of RAM that qualifies for Windows 7.
I have Windows XP 32-bit Professional in my bootcamp partition and wanted to know if I could buy an upgrade for a clean installation of a 64-bit Windows 7 or if I needed to buy the new copy of Windows 7 which is more expensive. According to Windows, you can upgrade from XP if it is a clean installation, but I don't know if this holds for bootcamp partitions.
My current partition for Windows XP is 32GB and wanted a bigger partition which a clean installation would let me do, I reckon.
Any help would be awesome and well-appreciated! Thanks in advance for your time

Yes, you can do a clean install.

Simply do not enter the product ID when prompted. Instead, allow the install to complete. Then, install the Boot Camp software (you'll need the version that comes with the Snow Leopard disc) and then install Windows updates. When finished, manually kick off Product Activation. At that point, enter your Product ID and all should be well.

If not, the worst case scenario is that you'll need to reinstall Windows 7 on top of the existing install.

Ringoya,

Please note that when migrating from Windows XP to Windows 7 you will not have an "in place upgrade" option. You will however have the option to select "custom" install when prompted. The Windows 7 install process will then copy all of your data in "My Documents" over to a Windows.old folder within Windows 7 itself. All applications and documents stored in other locations will have to be reinstalled / transferred manually.
For more information on the Windows 7 Upgrade, please go here: Installing and reinstalling Windows 7
For additional assistance with the migration of Windows XP to Windows 7, please go here: Windows 7 RC | Support, Deployment, Resources

Jessica
Microsoft Windows Client Team