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So I already have 4 partitions and it seems that i have a mbr disk and I want to convert it to gpt but I'm using AOMEI pro and when I want to convert i get a message saying to check if my motherboard supports UEFI/EFI like this: http://www.disk-partition.com/articles/images/mbr-partition-table-to-gpt/mbr-partition-table-to-gpt4.gif I checked my Panther folder From Windows and seems like it supports BIOS.The question can i convert using AOMEI still or im gonna lose the disk , destroy the windows. If i cant how can i install Ubuntu without deleting one partition because i cant.

  • Instead of converting to GPT, which I don't think is possible, you can instead convert one of your primary partitions to a logical partition as described here. – TheSchwa Feb 25 '16 at 20:10
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You can convert from MBR to GPT form with my gdisk program, which comes in the gdisk package in Ubuntu. The process is documented in detail here.

HOWEVER, doing so will render Windows unbootable -- at least, unless and until its BIOS-mode boot loader is replaced with an EFI-mode boot loader. This is a moderately complex task in and of itself. If you want to pursue it, check out this blog, which describes the process in detail. Note that converting from a BIOS-mode to an EFI-mode boot requires support in your motherboard. If you're booted in BIOS mode, you really can't tell if this support is present from within Windows; you must reboot into the firmware setup utility and look for telltale options, such as just about any mention of "EFI" or "UEFI"; "legacy-mode booting" or a similar term; or "Secure Boot." Most PCs introduced since mid-2011 support EFI. Any computer that shipped with Windows 8 pre-installed and with a Windows 8 sticker on it should use an EFI (a UEFI, in fact -- UEFI is just EFI 2.x).

Instead of converting Windows to boot in EFI mode, you can probably either delete one of your partitions or convert one from primary to logical form, as others have suggested. My FixParts program (also part of the gdisk package in Ubuntu) can convert from primary to logical. There are constraints, but as you must resize at least one partition to install Ubuntu, these shouldn't be too onerous. You must be cautious, though -- Windows will boot only from primary partitions in BIOS mode, so you must not convert a boot partition (either your regular boot partition or an emergency boot partition).

One final twist: If your computer does use an EFI, using BIOS for dual-booting presents its own risks. The biggest risk is that you may accidentally install one OS in BIOS/CSM/legacy mode and the other in EFI/UEFI mode. This sort of cross-mode installation is difficult to get working. See this page of mine for details. Thus, if you find that your computer has an EFI, you might want to consider converting Windows from BIOS-mode to EFI-mode booting, even though it's likely to be the harder approach in the short term, in the interest of greater long-term flexibility and less chance of stumbling into a cross-mode boot nightmare. This is admittedly a difficult dilemma, though; the odds of encountering a complication with either path are higher than I'd like.

Another alternative is to install Ubuntu in a virtual machine (VMware, VirtualBox, etc.), which will bypass partitioning and boot-mode problems.

  • Thank You for your time and explanations , I installed VMware . – Sele Feb 26 '16 at 17:08
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Ubuntu works on both legacy (msdos) and UEFI (gpt) - So it you don't really want to use gpt you don't have to.

  • the problem is that i already have 4 partitions soo When I create another one by shrinking one up by 100GBs , it shows as unusable because as i read , i can only have 4 primary partitions on mbr ... In the end i cant install ubuntu alongside Windows 10 – Sele Feb 25 '16 at 18:17
  • Oh, I see. Are you sure you can't spare any of them? I have 4 partition on my UEFI(gpt) Windows 10 disk (i have two disks) and one of them is UEFI partition, so you should only have 3? – Joakim Koed Feb 25 '16 at 18:23
  • These are my partitions C-> Windows and some Programs , E->Apps ,Games,Music and rest of Programs . The other 2 came with W10 .. postimg.org/image/iow86n9ul – Sele Feb 25 '16 at 18:30
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    I see.. One option I can think of (if its possible for you) transfer everything from E: to an external HD, then create one primary boot for ubuntu and one logical NTFS-drive. Then both Windows and Ubuntu and share the "new" drive. – Joakim Koed Feb 25 '16 at 18:39

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