BIOS can limit your partition, UEFI give you way to make your sizing beyond the limit

The storage industry has recently introduced storage devices with capacities which exceed 2TB (2 trillion bytes). In order for a system to fully support capacities greater than 2TB, the device must be initialized using the GPT partitioning scheme to support addressing the full range of capacity. If the user is intending to boot from one of these large disks, there is an additional requirement that the system’s base firmware interface must be using UEFI and not BIOS. This Knowledge Base article outlines Microsoft’s support statement across Windows versions since Windows XP, and the requirements necessary to address the full capacity of these devices.

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