The 620 is compatible with the biggest hard drives available today (4tb?). However, a UEFI BIOS is required to boot from a drive of greater than 2.2tb capacity.

I think my BIOS is made by American Megatrends.

How do you come by this capacity figure?

Simple: every machine, Dell or otherwise, new or old, that I've tried a 4tb in has recognized the capacity fully. SATA limits, whatever they are, are far beyond the capacity of current storage technology.

The 2.2tb limit is due to the old Master Boot Record (MBR) format's maximum sector count of 2^32 * 512-byte sectors.

Beyond 2.2tb REQUIRES 64 BIT OS,  INTEL RST 10.3.X or higher, AND GPT partitions via UEFI Bios. The Inspiron 620 does not support the INTEL RST or GPT partitions.

3rd party Controllers with extra software do allow larger drives but not Bootable drives.

If your system uses an early Intel RST driver, your 3TB disk drive may appear to be 800GB.

Seagate DiscWizard software installs a device driver to achieve full capacity on Legacy BIOS systems.

Windows systems with legacy BIOS using DiscWizard will need two partitions on the boot drive to achieve full capacity.

Windows 7 and Vista native support for 3TB non-booting data drives is with GPT partitions, available on all systems.

Windows 7 and Vista native support for booting 3TB is on UEFI BIOS systems and using GPT partitions only.

http://www.seagate.com/support/downloads/beyond-2tb/

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Beyond 2.2tb REQUIRES 64 BIT OS,  INTEL RST 10.3.X or higher, AND GPT partitions via UEFI Bios. The Inspiron 620 does not support the INTEL RST or GPT partitions.

Large drive support is an OS function (Vista or later). booting requires UEFI and a 64-bit operating system; data use only can be done with either 32- or 64-bit.

I've used large drives with old Dells like the E310 and 2350. No special software was required.

So I take it that I can add  a very large drive (up to 4TB - with no added software or hardware) as long as I use it for storage?

So I take it that I can add  a very large drive (up to 4TB - with no added software or hardware) as long as I use it for storage?

64 Bit OS is required for drives larger than 2TB

INTEL RST Greater than version 10.1 is required for drives Larger than 2TB

http://knowledge.seagate.com/articles/en_US/FAQ/218615en

Like other kinds of software, the Intel RST drivers are updated to keep pace with new technology. The Intel drivers found in retail releases of Windows 7 have a 2.2TB limitation. Rather than cut off the capacity at 2.2TB, the limitation expresses itself as the remainder above 2.2TB. In other words, the driver causes the Windows operating to see a 3TB drive as 746.52 GiB (or 800GB).

With 32 bit OS Both the partition length and partition start address are stored as 32-bit quantities.
Because the block size is 512 bytes, this implies that neither the maximum size of a partition
nor the maximum start address (both in bytes) can exceed 2^32 × 512 bytes, or 2 TiB

http://msdn.microsoft.com/en-us/windows/hardware/gg463525.aspx

The GUID Partition Table (GPT) was introduced as part of the Unified Extensible Firmware Interface (UEFI) initiative. The maximum partition (and disk) size is a function of the operating system version. Windows XP and the original release of Windows Server 2003 have a limit of 2TB per physical disk, including all partitions. For Windows Server 2003 SP1, Windows XP x64 edition, and later versions, the maximum raw partition of 18 exabytes can be supported. (Windows file systems currently are limited to 256 terabytes each.)

64 Bit OS is required for drives larger than 2TB

Vista or later, both 32- or 64-bit, can partition and format large drives.

I have confirmed this with a Dimension 2350 (Windows 7 32-bit.) and a 3tb Hitachi (both internal and eSATA).

http://www.seagate.com/support/downloads/beyond-2tb/

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[quote user="SpeedStep"]64 Bit OS is required for drives larger than 2TB

Vista or later, both 32- or 64-bit, can partition and format large drives.

(True but they CANNOT BOOT from these drives with any 32 bit os)

Drives larger than 2.1TB REQUIRE Driver / Bios support for GPT partitions.

I have confirmed this with a Dimension 2350 (Windows 7 32-bit.) and a 3tb Hitachi (both internal and eSATA).

[/quote]