It possibly ships with a 64-bit EFI implementation. An EFI can boot only 64-bit OSes in EFI mode.
So to boot a 32-bit version of Windows, you must boot it in BIOS mode. Microsoft has decided that it won't support booting in BIOS mode from GPT disks
This requires converting the partition table ( the entire partition table; not just a single partition) from GUID Partition Table (GPT) to Master Boot Record (MBR).
bootia32 I believe is only for the Itanium-based computers.