I had a 3TB Toshiba internal hard drive. I wanted to be able to use all 3TB in Windows 7. Microsoft informed me that Windows 7 supported both MBR and GPT partitioning schemes, and both BIOS and UEFI system firmware; and, further, that GPT partitioning would permit full access to drives larger than 2GB, but would permit booting from a drive larger than 2GB only if (a) it was a 64-bit version of Windows and (b) the firmware was UEFI rather than BIOS.
That sounded good. But when I did what I thought I was supposed to do, diskmgmt.msc (i.e., Disk Management) said that I had an unallocated GPT volume of only 746.39GB. It seemed my efforts had not led to the desired 3TB volume. I flailed around on Toshiba’s website for a while, made calls, bounced from one number to another, wound up with a Toshiba internal drive tech support number (510-651-6798), called that number repeatedly, and it rang until finally the phone or something shut it off. I concluded that Toshiba was not going to help me, and either I would have to find a solution on my own or get rid of the drives.
What was supposed to happen, in my understanding, was that initializing the drive was supposed to create that glorious 3TB space. Since initializing had failed to do that, I reasoned, I should try to re-initialize. A search led to a suggestion to use a Diskpart command to clean the disk and remove all MBR and GPT information. The way to do this was to look again at Disk Management. It said that the target drive was Disk 3, and that it was Online. If offline, I’d have had to right-click that left gray bar and make it online. Now, using an elevated command prompt shortcut, I ran Diskpart (by just typing Diskpart at the prompt). Within DISKPART, I needed to run a LIST DISK command. For purposes of Disk 3, its output matched that of Disk Management: Online, 746GB, GPT. Next command: select disk 3. It looked like I was all set to work on disk 3. Next, I chose the Clean command; they said that Clean All would take three hours per terabyte, whereas Clean was finished almost instantly. I ran List Disk again. It had removed the GPT indication, but it still saw only 746GB. Disk Management likewise said 746GB, and also said Not Initialized. A right-click > Initialize Disk > GPT did not change the reported size. So the Diskpart approach was a bust.
Someone else said the solution was to use updated Intel Rapid Storage Technology (RST) drivers. But Control Panel > Programs and Features said I was using version 12.8, and that version was only a few months old — far more recent than the post recommending an update. It seemed likely that I already had adequately updated RST drivers. I was going to download and install version 12.9 anyway, but decided this really made no sense: it was a RAID driver, and I was not running RAID, and the download page also offered a warning: “Before installing this application or requesting technical support from Intel, first contact your system manufacturer. They typically provide software which is specifically configured for your system.” But I thought, what the hell. I uninstalled version 12.8 and, after a mandatory reboot, tried to install version 12.9. Thing is, I could not figure out how to install it. Contrary to its read-me file, there was no included .EXE file, and right-clicking on the included INF files did not run them. I reasoned that maybe the RST software itself was the problem, and took another look at Disk Management. Alas, no joy: disk 3 was still a 746GB partition. It occurred to me that perhaps Control Panel > Windows Update would rescue me from whatever mess I had just created, but no, there seemed to be nothing there for me.
There was also the possibility that a BIOS update would fix everything, but I didn’t think that was likely. Someone pointed out that I could boot the computer using a bootable USB drive and take a look at the drive using Linux. That was true, but I decided to postpone that when a different thread raised another possibility. I was attempting to work with this 3TB drive by putting it into an external enclosure, connected to the computer via USB cable. I had already seen a few puzzling comments in which people thought there might be a difference when they put the drive inside a desktop computer; this thread presented the notion that not many external enclosures were able to work with drives larger than 2TB. Well, that was the answer, simple enough: specifications for my Rosewill RX-DU100 external drive bay put its limit at 2TB. I bought a SYBA CL-ENC50038 USB 3.0 bay and tried that. Sure enough, Disk Management now reported 2794.39GB. Wow, lots of lost overhead out of the alleged 3GB, but still better than nothing. Disk Management offered to convert it to an MBR drive, when I right-clicked on the gray area on the left side, but again GPT was what I wanted. I right-clicked on the crosshatched space at the right side of Disk Management and created a new simple volume with the full 2794GB. Done!