This will occur if you install Windows 7 and manually try to create one partition using “Advanced Drive Options” during setup.
Note: The check for UEFI and GPT is not done during Setup in Advanced Format like it is done in Disk Management.
If you install Windows 7 x64 on a system that supports UEFI you can partition the drive to use GUID Partition Table (GPT) and access all of the drive if the system is in UEFI mode.
Important: The disk that you select must not contain any data. Back up the data, or move your data to another volume before performing operations in diskpart.
In order to Boot a UEFI enabled system the disk type should be changed to GPT using convert gpt command. Follow steps as below.
1. Press Shift+F10, this brings a command window. At command prompt, run the Diskpart.exe (This starts the diskpart console. After the console is initialized, DISKPART> is displayed. The diskpart console is now ready for input commands.)
2. Under diskpart> prompt type “list disk”. (Locate the disk, in this case disk 0)
3. Type "Select disk 0" (This selects the disk that you want to convert to GPT.)
4. Type "Convert GPT" (This command will convert drive to GPT.)
5. Just to make sure everything went fine type “list disk”. The converted disk should now have a asterix in the GPT column. (See example image below)
6. Type exit and exit again. This should close the command window.
Select the disk you have just converted and that should display as “Unallocated Space”.
The installation process should start and proceed as usual. After reboot the Windows 7 x64 should be installed on the GPT partitioned disk.
For details on Windows support for large drives see Knowledge Base article:
2581408 Windows’ Support for Disks with Capacity Greater than 2TB
814070 How to establish and boot to GPT mirrors on 64-bit Windows
297800 HOW TO: Use the Diskpart.efi Utility to Create a GUID Partition Table Partition on a Raw Disk in Windows
Using GPT Drives
Article ID: 2604034 - Last Review: Sep 23, 2011 - Revision: 1