http://answers.microsoft.com/en-us/windows/forum/windows_7-performance/i-have-a-3-tb-drive-windows-7-ultimate-wont-format/b1cc3811-f25f-e011-8dfc-68b599b31bf5?auth=1
From the above MS Forum thread:
"To use any drive over 2.19 TB you will need:
- A computer using Windows Vista or later (Windows XP isn't compatible with GPT formatted disks, so it can't see them)
- A sata controller that is compatible (to find out if it is compatible, find out what motherboard or add-on board SATA controller you have and google it-e.g. Intel ICH8 3TB )
- A drive that is larger than 2.19 TB
So, if you know that you meet all three of the above requirements, follow proper installation procedures with installing a new drive and just hook it up. Depending on where you bought the drive and if it is OEM or Retail it may or may not come pre-formatted with an NTFS partition of 2TB (this is for convenience to keep people from getting upset when they hook the drive up and it doesn't appear in My Computer).
Now, go to Control Panel, Administrative Tools, Computer Management. Choose Disk Management on the left and you should see in the lower portion of the screen a list of your installed drives. The larger drive should appear in the list with a capacity displaying on the left. Note, a 3TB drive will only have a storage capacity of LOWER than 3TB (read: when you add formatting and a file system, both of those require space on the drive, so you will not have a full 3TB of space to use-this is the nature of hard drives-you will never have the full stated capacity-ever since it is required to make the drive useable).
Now, assuming you're using it as a data storage drive, ensure that nothing is still stored on it and right click on the partition on the right, right click the partition (if there is one on the drive already) and click "Delete Volume".
Next, right click on the name on the left "Disk #" and choose "Convert to GPT Disk". Now this should allow you to right click on the unformatted space on the right and to create a new partition which can hold the full available capacity of your drive.
This should work with all versions of Windows Vista and Windows 7 (with the only exception being a starter edition *may not*).
With the variety of systems now sold using UEFI instead of BIOS, you can today on those systems install Windows directly onto a drive greater than 2.19TB in size. Just ensure that your computer actually is using it before attempting to run Windows on a drive that large. It's also probably not a great idea just due to the fact that if Windows fails you will likely lose all the data on that partition."
