There is a utility, for Windows, Linux, and Mac, which will convert MBR disks to GPT without destroying data. (Please note that it does NOT preserve data if you’re using an “extended” partition!!!!) It is called “GPT fdisk”, and it is here:

http://www.rodsbooks.com/gdisk/download.html

Binaries for Windows can be downloaded here:

https://sourceforge.net/projects/gptfdisk/files/latest/download

In Windows, gdisk.exe needs one parameter, which is a drive number followed by a colon. Drive numbers are not letters; they can be obtained using the GUI Disk Manager or using ‘list disk’ in DISKPART on the command line.

C:\Documents and Settings\Administrator>diskpart

Microsoft DiskPart version 5.2.3790.3959
Copyright (C) 1999-2001 Microsoft Corporation.
On computer: SITEFS

DISKPART> list disk

  Disk ###  Status      Size     Free     Dyn  Gpt
  --------  ----------  -------  -------  ---  ---
  Disk 0    Online       232 GB  8033 KB
  Disk 1    Online       466 GB      0 B
  Disk 2    Online       932 GB      0 B
  Disk 3    Online       931 GB      0 B
  Disk 4    Online       931 GB      0 B

DISKPART> exit

All you have to do to convert, is to run gdisk on a given drive:

gdisk 3:

say yes to all of the prompts, and then use the single command “w” for “write” the new partition table, and confirm. Then you will need to restart the “Virtual Disk” service if it’s running:

sc stop vds
sc start vds

and then test your results using DISKPART from the command line; the GPT disks will be starred as such.

DISKPART> list disk

  Disk ###  Status      Size     Free     Dyn  Gpt
  --------  ----------  -------  -------  ---  ---
  Disk 0    Online       232 GB  8033 KB
  Disk 1    Online       466 GB      0 B
  Disk 2    Online       932 GB  2550 KB        *
  Disk 3    Online       931 GB  2173 KB        *
  Disk 4    Online       931 GB  2173 KB        *

DISKPART>