Delete an EFI Partition from Windows 7

The Windows 7 Disk Management tool has issues deleting those pesky EFI partitions so commonly found on Mac-formatted drives. Use the diskpart command utility instead.

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Windows\system32>diskpart

Microsoft DiskPart version 6.1.7601
Copyright (C) 1999-2008 Microsoft Corporation.
On computer: RAY

DISKPART> list disk

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online          465 GB      0 B
  Disk 1    Online         2794 GB  2794 GB        *

DISKPART> select disk 1

Disk 1 is now the selected disk.

DISKPART> list part

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    System             200 MB    24 KB

DISKPART> select part 1

Partition 1 is now the selected partition.

DISKPART> detail part

Partition 1
Type    : c12a7328-f81f-11d2-ba4b-00a0c93ec93b
Hidden  : Yes
Required: No
Attrib  : 0000000000000000
Offset in Bytes: 24576

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
* Volume 6                      RAW    Partition    200 MB  Healthy    Hidden

DISKPART> delete part override

DiskPart successfully deleted the selected partition.

DISKPART> exit

Leaving DiskPart...

Source: http://superuser.com/questions/56958/can-i-delete-efi-system-partition-without-harming-other-data-on-drive