Ubuntu 12.04 installer and gparted do not detect the existing windows partitions [duplicate]

Solution 1:

I'm the author of gdisk, and I agree with what psusi has written, with the caveat that I can't know what's really on /dev/sda5, so I can't say if it's safe to remove it. If it's the stuff that you've burned to your recovery DVDs, it should be safe to delete it, though.

If there's sufficient free space on /dev/sda5 (about 17 KiB), you should be able to resize the partition using GParted or a Windows tool, IF that tool doesn't flake out because of the illegal partition table. You might be better off backing it up to another disk, deleting it, and then restoring it. You'll need to use a backup/restore method that enables restoring to a smaller partition, though. (Alternatively, you could shrink /dev/sda4 by just a bit to make room to create a new /dev/sda5 that's as big as it is now.)

Also, on an unrelated matter, you seem to have a UEFI-based PC. On such systems, the advice to install Linux second isn't as important as it is on BIOS-based systems. (U)EFI still has a lot of flaws, but despite those problems, it's got much saner boot management than does BIOS, and Windows behaves itself better with respect to other OSes on EFI than it does on BIOS.

You might want to use gdisk to change your Linux partitions' type codes from 0700 to 8300 to keep them from showing up as unformatted disks in Windows. See here for more on this issue.

Solution 2:

You are using GPT, not MBR, and gdisk told you what you need to do:

You will need to delete this partition or resize it in another utility.

It isn't quite clear which partition it is referring to, but that would be the last one, or number 5 in your case. It runs right up to the very last sector of the disk, which is not allowed since the GPT stores a backup copy in the last 33 sectors of the disk. If there isn't anything important on the partition, you should be able to just delete it in gdisk.