Partitioning a 3TB drive for Boot Camp.

Question

I have a Mac Pro, with two drives installed. The first drive is my OS X boot drive. The second drive is (or will be) a combination of Windows XP, and empty space for OS X. This latter drive is a WD 3TB Green drive. Because of the limitations in XP (and BIOS booting), the XP boot partition must be in the first 800 GB.
If I try to create a single partition using Bootcamp Assistant, it insists on using the entire drive. If I create an OS X partition and then use Bootcamp Assistant, it puts the Windows partition at the END of the drive. I can almost do what I want using manual (command line) partitioning, but then VMware Fusion will not allow me to set up the bootcamp partition for use as a virtual system.
Is there any sequence - command line or Apple-supplied GUI utility, I don't care which (I'm a Unix sysadmin by trade; the command line doesn't scare me) - which will let me set up a 500 GB bootcamp partition at the start of the drive; get Windows installed in it; and get the partition loaded into VMware as a virtual machine, with the remaining space setup as a journaled HFS+ volume?
If not, I guess I'll have to bite the bullet and buy Windows 7. Sigh ...

Answer 1

The problem is not the version of Windows as much as it is having to put MBR and GPT on the same disk. This gets really complicated quickly, and hybrid MBRs are non-standard and not safe. Even Apple's own documentation says that they aren't safe.
http://developer.apple.com/library/mac/#technotes/tn2166/_index.html
However, because of how Apple's firmware is implemented, to use Windows, a hybrid MBR is effectively required if you're going to share a single disk of this size between Windows and Mac OS. You're better off using 2TB or smaller disks.
1. MBR has a disk (not partition) size limit of 2.2TB.
2. Because this is a 2.2TB+ drive, you need GPT to see the remaining space at all.
3. Apple hardware is EFI, but uses a CSM-BIOS mode for booting Windows of all versions.
4. When Windows is booted in CSM-BIOS mode, it requires MBR.
5. A disk only need to be GPT if it is greater than 2.2TB, or if you intend to *install* Mac OS X on it.
Now, if this were a 2TB drive or smaller, you could just use MBR only. And you could partition the first 800GB or whatever for Windows, and the rest as jhfs+ for Mac OS. Mac OS X is perfectly content using an MBR only disk, so long as you aren't asking to install Mac OS X onto it.
So you've kinda got yourself into a pickle with this giant single disk. Anyone else trying to do this even with Windows 7 will also be afflicted.
You can specify 500GB in the MBR for Windows, and Windows will use it just fine because it ignores the GPT anyway. But Mac OS X does not ignore MBR in favor of GPT or vice versa. If both MBR and GPT are on the disk, there's a set of rules for determining which partition map it should believe. According to the UEFI spec, an MBR with more than one entry, or a single entry that is not type EE, is *NOT* a GPT disk. It is an MBR disk.
In any event, the 2nd partition entry for the rest of this space in the MBR cannot match up with the same space in the GPT because the MBR is 32-bit limited. It can't correctly describe the full space for the disk, so by design it won't be in sync. Now, I don't have a 3TB drive to test Mac OS X's behavior with at the moment, but past experience tells me it will defer to the MBR entry unless it is type EE. Any sectors specified as type EE, then Mac OS X will defer to the GPT.
So anyone using 2TB+ disks is in for a world of hurt unless and until Apple moves from Intel EFI 1.10 to UEFI 2.x so that Windows 7 or 8 64-bit can boot in UEFI mode. And then, MBR will not be required at all. And this problem won't exist.