Craig notes that most existing systems cannot handle capacities greater than 2.1TB because of the original logical block addressing (LBA) standard developed by IBM and Microsoft 20 years ago. "Nobody expected back in 1980 when they set the standard that we'd ever address over 2.1TB."
To get around this limitation, Craig says that Long LBA is necessary to increase the number of bytes used to define an LBA address in the command descriptor block. Fortunately, 64-bit versions of Windows 7 and Vista are compatible with Long LBA, though, users of older versions are out of luck.
Although 32-bit builds of XP will see 3TB drives, in-house tests show that as little as 990MB is available while the remaining bytes are inaccessible. Craig also says that current master boot record partitions are limited to 2.1TB, so a GPT partition table would be necessary to use a 3TB HDD as a boot drive.
GPT and a larger LBA addressing scheme are part of Intel's Extensible Firmware Interface, a BIOS replacement that has yet to become standard and is only present in a handful of motherboards. Along with UEFI-compliant motherboards and 64-bit operating systems, new RAID controllers and drivers will also be required.