You've come to this page because you've said something similar to the following:
The only way to convert from a disc partitioned with the MBR partition table scheme to the EFI partition table (also known as the GUID partition table, or GPT) scheme is destructively. You have to delete all existing partitions from the disc before converting.
This is the Frequently Given Answer to such statements.
That is false. It is quite possible to non-destructively convert from the
MBR partition table scheme to the EFI partition table scheme. At least
two tools exist for doing so — one published and one (currently) not.
Microsoft's Disk Manager and diskpart have the
limitations of only being able to convert empty discs. But they are far
from being the only tools capable of converting partition tables, and the
other tools available don't share Microsoft's limitations.
Here's the unpublished tool
(dasdpart)
in action, demonstrating such a conversion:
[H:\]dasdpart
[H:\]inspect 0|head /11
Disc GUID: 00000000-3d1b-17e3-8201-020000000000
The partitionable area is blocks 1 to 60067034 inclusive (28.6GiB).
1
0a IBM Boot Manager
0000003f-3d1b-17e3-8201-020000000000
63 16064 16002 7.8MiB
2
07 MS Data
00003ec1-3d1b-17e3-8201-020000000000
16065 16434494 16418430 7.8GiB
[H:\]mbrtogpt 0
[H:\]inspect 0|head /13
There are 4 entries in the partition table, using 1 sectors.
Partition entries are 128 bytes long.
Disc GUID: 6a2f4b65-4c19-473d-a401-5635953aa27a
The partitionable area is blocks 3 to 60067032 inclusive (28.6GiB).
0
083e58f1-ff57-4b08-9ab7-f7433966a104 IBM Boot Manager
652b4a10-aa9c-4e60-9ad5-0384abcf0a0d
63 16064 16002 7.8MiB
1
ebd0a0a2-b9e5-4433-87c0-68b6b72699c7 MS Data
5be8f61b-f6f3-4c30-b2cc-7c8ba8909c3d
16065 16434494 16418430 7.8GiB
[H:\]
The published tool is
Rod Smith's gdisk.
If you have a Linux, FreeBSD, or MacOS version 10 system, you can just run
it directly. If not, then notice that M. Smith lists two sources for
"emergency rescue" CD-ROMs that one can bootstrap a system with, which
contain gdisk.