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I have tried everything I can think of at this point and I'm at a total loss.

I have a 2TB drive I want to install Windows 7 and 11.10 (both are 64 bit) side by side, but once I install Windows it must need gpt to work or something because no matter how many times I've removed it, it always returns. If I use gdisk and set the disk as mbr, Windows won't load.

Now this last time I ran gdisk and tried to boot into Windows before I installed Ubuntu all the way and ended up at a grub rescue prompt. Any help please?

Also let me say I have been searching and reading for days and have tried everything I can find to make this work so this isn't a one time event, it's continual.

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4 Answers 4

To describe the situation with Ubuntu and Windows, allow me to give some background information.

When you install Ubuntu, it installs something called GRUB. This loads first and can load either Windows or Ubuntu. Windows has something known as NTLDR or MSLDR which can only load Windows.

Thus, install Windows first(booting from the setup disk), saving room for Ubuntu (at least 20GB, but you can go into the terabytes), or if the Windows setup system does not allow you to make a partition smaller than the free space, then use the whole drive.

Once Windows is installed, begin to install Ubuntu (booting into the live CD). Be sure to specify the side-by-side option, or use the advanced partition tool and fill the rest of the drive with one Ext4 partition (resizing Windows partition if necessary). Click on the free space and then add to do this. Also, be sure to set this partition to mount as /. If it does not let you select the mount point, click on the new(EXT4) partition and click edit at the bottom while the partition is highlighted to specify this. Allow Ubuntu install to finish fully.

When you reboot, you will be prompted to select between Windows and Ubuntu at startup (by GRUB), in which case you may select either.

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All that is a normal install however my issue arises with Ubuntu not recognizing the current Windows install. I know I need to install Windows before Ubuntu but Ubuntu see 2TB of free space rather than another OS... –  Bill.Caffery Apr 24 '12 at 23:48
This is a good explanation, however, the key words in the question are "2Tb" and "GPT". MBR has 2Tb limit so you (supposedly) can only boot from a 2Tb disk if it has GPT partition table. Which somehow causes problems for the author. –  Sergey Apr 24 '12 at 23:50
@Bill.Caffery Use the ubuntu install to install Ubuntu to your disk which should already have been made GPT by Windows from the testmode, and *instead of rebooting, run grub-install /dev/sda1 from a terminal(CTRL+ALT+T). This installs GPT grub. If Windows sets up as MBR, use johnlewis.ie/converting-to-gpt-in-ubuntu as a guide to Gdisk, and then use grub-install /dev/sda1. –  hexafraction Apr 25 '12 at 15:49

The usual cause of the symptom of Ubuntu's installer reporting a non-empty disk as having no partitions is a damaged partition table. Several distinct types of damage can cause this symptom. Some, but not all, of these involve stray GPT data on an MBR disk; others can occur on MBR disks or on plain GPT disks.

The MBR disk size limit is 2 TiB (2.2 TB), so a 2 TB disk is under that limit, and may use MBR. That's not to say that it does use MBR, though; it might use GPT. It's also possible that it was partitioned with GPT and then re-partitioned with MBR. Depending on the tools used, this can leave behind stray GPT data, which is one of the things that can cause the missing-partitions symptom. In this case, my FixParts program can fix the problem pretty easily.

Note that Windows ties its firmware boot mode to its partition table type -- if a computer uses a conventional legacy BIOS, Windows will only boot from an MBR disk; and if the computer uses a new-style UEFI, Windows will only boot from a GPT disk. Thus, even on a sub-2TiB disk, GPT may be required, if the computer uses UEFI and is configured to boot in UEFI mode. (Most UEFI firmware provides a BIOS compatibility mode, which can greatly complicate matters if you don't understand it.) Linux is more flexible; it can boot from a GPT disk using either BIOS or UEFI, and (in theory) from an MBR disk using either BIOS or UEFI.

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Is there a step-by-step solution to this problem? I have a 2TB disk. I installed Windows 7, leaving 1TB free for Ubuntu. When I insert the Ubuntu 12.04 CD hoping to install Ubuntu along side Windows 7, the installer fails to recognise the Windows 7 partition.

How can I run FixParts from a live CD? Has anyone experienced and successfully resolved this issue?

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Run grub-update after both installations are finished for GRUB to find Windows. Although it may seem like this would be automatic, it is not.

Also, when installing Windows, the installer chooses to put its boot-loader on a known partition that is not the system partition, so it could be anywhere. If you use that partition for Ubuntu you will destroy GRUB's ability to access the information it needs to dual boot.

To avoid the situation determine you Windows partition during install and DO NOT create any other partitions at this time, forcing Windows to put it where it actually belongs. Install Ubuntu and run grub-update to make sure Windows loader is available and gets found.

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ok i dont seem to be making my issue clear... grub is NOT the problem... i cant even get the ubuntu installer to recognize that windows is installed therefore i cant get ubuntu installed let alone worry about grub... –  Bill.Caffery Apr 25 '12 at 1:01

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