Hello,

I do a great deal of work with virtual machines and perform all of my operating system development on virtual platforms. My desktop PC came with a 500GB hard drive. Using a virtualization program and creating a couple of production sized virtual machines will take up a great deal of that space very quickly.

A larger hard drive is one of the easiest upgrades one can make to a computer. I ordered a 3TB drive for my Dell OptiPlex 990 and had hoped to just plug and chug, but it didn’t work out that way. What I had found out that the default traditional method of BIOS hardware management on the PC only allowed it to see partitions or drives no larger than 2TB. BIOS-based computers use hard drives that are partitioned in the Master Boot Record or “MBR” format. To use the new crop of large drives with more than 2TB of space, one needs to format the drive as a GUID Partition Table or GPT device. There, the largest of drives can be partitioned and formatted as one single volume, which is what I was after.

I should have just done my homework and just ordered a 2TB drive. Under BIOS/MBR, Windows setup would only see 2TB, leaving around 768GB unavailable. GPT disks cannot use the BIOS system. They rely on a newer system called the Universal Extensible Firmware Interface, or “UEFI.” The OptiPlex 990 has the ability to use a BIOS-based system or UEFI, but not both. Each are mutually exclusive to the OptiPlex 990. Newer computers have the ability to use UEFI with support for legacy BIOS system (UEFI-CSM), but not the 990.

I initially tried to get the 3TB HDD to be recognized by booting to a Windows PE boot drive and use DISKPART to partition and format the HDD as a GPT disk. Still, Windows setup would not use the drive. Windows 10 setup would indicate that setup could not use any available partition as they were in GPT format. The problem wasn’t the drive, which was set up correctly, it was the install media. I use an 8GB USB key drive to install Windows from an ISO file. A great piece of freeware called “Rufus” is what I use to make the boot-able USB key from the Windows ISO file. Rufus defaults to creating a Windows PE volume, which is what Windows setup is, that supports both MBR and UEFI with backwards compatibility. I though that would work, and it should have, but the OptiPlex 990 was BIOS or UEFI, not both. One option to create the USB boot key was pure UEFI.

While I was sorting this out, I noticed that when I switched the 990’s BIOS to UEFI mode, there were no more boot-able drives like the HDD, CD/DVD, or USB listed. This was accurate because none had been made available. The 3TB drive was GPT but did not contain any boot-able volumes at that point. I had yet to make a pure-UEFI USB key, and there was no disc in the DVD-RW drive, so no there were no UEFI boot options. Any and all BIOS/MBR, and UEFI/GPT boot devices are shown when the PC POSTs. As soon as I partitioned and formatted the 3TB drive as GPT, and inserted the all-UEFI USB boot drive, the OptiPlex 990 saw the USB drive as a UEFI boot device and Windows setup accepted the partitioned 3TB drive for install. After that, Windows 10 installed and I had ALL of the available space, which came in around 2.78TB.

To do…

Partition/format the drive as a GPT device.

Create a boot-able Windows PE USB drive and boot the target computer to it, with the larger-than-2TB-HDD installed.

Run DISKPART from the Windows PE prompt and enter the following commands to partition and format the drive as a GPT disk, minus the REM statements.

select disk 0
clean
convert gpt
rem == 1. Windows RE tools partition ===============
create partition primary size=300
format quick fs=ntfs label="Windows RE tools"
assign letter="T"
set id="de94bba4-06d1-4d40-a16a-bfd50179d6ac"
gpt attributes=0x8000000000000001
rem == 2. System partition =========================
create partition efi size=100
rem    ** NOTE: For Advanced Format 4Kn drives,
rem               change this value to size = 260 ** 
format quick fs=fat32 label="System"
assign letter="S"
rem == 3. Microsoft Reserved (MSR) partition =======
create partition msr size=128
rem == 4. Windows partition ========================
rem ==    a. Create the Windows partition ==========
create partition primary 
rem ==    b. Create space for the recovery image ===
shrink minimum=15000
rem       ** NOTE: Update this size to match the size
rem                of the recovery image           **
rem ==    c. Prepare the Windows partition ========= 
format quick fs=ntfs label="Windows"
assign letter="W"
rem === 5. Recovery image partition ================
create partition primary
format quick fs=ntfs label="Recovery image"
assign letter="R"
set id="de94bba4-06d1-4d40-a16a-bfd50179d6ac"
gpt attributes=0x8000000000000001
list volume
exit

Script from Microsoft

Create the all-UEFI Windows install USB drive…

Go into the computer’s BIOS by pressing F2 during the boot sequence (Dell), before Windows even starts to load. NOTE: BIOS/MBR disks will not boot in a UEFI/GPT configuration. Any change from BIOS/MBR to UEFI/GPT WILL REQUIRE a Windows reinstall. No way around it, so Back up your data.

On a separate computer, insert the USB key, and open Rufus as an admin.

The USB key should be listed in the top dialog box, make sure you’re formatting the right drive if there are multiple USB drives currently inserted into the PC. From the bottom part, near where it says “Create boot-able disk using [ ISO Image]”, click the small button with the disc and drive icon and choose your Windows install ISO.

Next, select the drop-down menu option under “Partition scheme and target system type”, choose “GPT partition scheme for UEFI.” If the source ISO file changes, the partition scheme changes also, so watch that.

Create the drive and insert it into the computer that has the large HDD and boot to it by pressing F12 (Dell/Lenovo). If the USB key was created properly as a UEFI device, it will show up as a UEFI boot option under the BIOS boot options which will still be the CD/DVD drive and the HDD (possibly).

Install Windows and relish in the large space now available!