My question is what are the drawbacks of running the 32-bit version of Windows XP on dual quad-core Xeon processors? Will the OS be able to utilize the 4-cores in both processor?

VirtualBox is flexible enough to handle many types of 32-bit and 64-bit configurations. If you need to run a 32-bit version of XP in a 64-bit host, you can do that without any problems.

Office 2010: Windows XP (32-bit only), Windows Server 2003 R2 with MSXML 6.0 installed, Windows Vista SP1+, Windows Server 2008 SP2+, Windows 7, and Windows Server 2008 R2.

So, while you can install 32-bit Windows XP (or 32-bit Vista or 32-bit Windows 7) as guests inside the Windows Virtual PC environment (which is, after all, a generic VM solution with some ...

Release Candidate 1 (RC1) of Windows XP Professional x64 Edition is now available: ZDNet has put Build 1289 through its paces.