After adding a hard disk to my computer today, I found out that you can't have more than four MBR disks in your Windows operating system (even x64 versions!) and that MBR partitioned disks have an upper limit of 2 Terabytes! Normal (x86 & x64) Windows operating systems (Pre-Vista SP1) cannot boot from GPT partitions. It is unlikely that the standard version (32-Bit) of Windows XP will ever boot from GPT partitioned disks.

What does this mean? Unless Microsoft fixes/patches this for Windows XP, your boot drive cannot be larger than 2 terabytes. Since this size of hard disk is already in the market, I found it interesting enough to comment on.

Resources Below:

Windows and GPT FAQ

Extensible Firmware Interface (EFI) and Unified EFI (UEFI)

Everything you want to know about GPT for Microsoft Windows with Itanium Processors