Dual-Boot – GParted and Ubuntu Installer Not Recognizing Windows Partition

First, GPT is not, in and of itself, the problem. The error you report (no partitions appearing in the installer) is indicative of a partition table problem. It's a long-standing bug of libparted (which the installer uses) that broken partition tables show as if they were blank disks. GPT is supported by libparted, though, and Ubuntu will install to GPT disks.

The key is this:

/dev/sda1 ends after the last sector of /dev/sda

This error message refers to the GPT's protective MBR, which is a "fake" MBR partition table that exists just to keep GPT-unaware utilities from using the disk. Your protective MBR contains a protective 0xEE partition that's too big. This really doesn't matter, but it's triggering libparted's "broken partition table" bug.

The solution is to fix the protective MBR. This is easily done using gdisk or sgdisk, which are part of the gdisk package in Ubuntu; however, I'm not sure if that package is installable in a live CD. Therefore, I'll tell you how to do this from an emergency disk:

1. Download Parted Magic and burn it to CD.
2. Boot Parted Magic.
3. Launch a terminal window (the icon of a monitor on the bottom of the screen).
4. Type gdisk /dev/sda to launch gdisk. You should see some startup messages and a prompt that reads Command (? for help):.
5. Type p in gdisk to view your partition table and verify that everything looks OK. If you see weird partitions, exit by typing q.
6. Type x to get to the experts' menu. The prompt should change to read Expert command (? for help):.
7. Type n. This generates a fresh protective MBR. The program will respond merely by displaying a new prompt.
8. Type w to save your changes. The program will warn you it will overwrite your old partitions and prompt you for confirmation. Respond y.
9. Reboot and try installing again. It should now work fine.

One caveat: Your computer is booting Windows in EFI mode, so you should also install Ubuntu in EFI mode. This is sometimes trouble-prone. I recommend backing up your EFI System Partition (ESP; /dev/sda1) while you're in Parted Magic or by using the Ubuntu installer. If you have problems after installing, you may need to install a new boot loader. See my EFI Boot Loaders for Linux page for details.

There's no such thing as a "GPT partition" in quite the sense that you seem to be suggesting. The GUID Partition Table (GPT) is a partition table -- that is, it's a data structure that defines partitions. The entire disk must be either GPT or something else, such as the older Master Boot Record (MBR) partition table. Thus, deleting the GPT data would delete all the partitions on the disk, which you probably don't want to do.

That said, some disks are actually MBR disks but they have leftover GPT data from an earlier partitioning of the disk. This situation can cause parted, GParted, the Ubuntu installer, and some other tools to mistakenly believe that the disk is empty. The FixParts program that you mentioned can detect and correct this problem. I don't believe this is your problem, though; computers that ship with Windows 8 almost always use GPT, so unless you re-installed Windows using MBR, your disk should legitimately be GPT. You can test this by running FixParts on the disk; if it terminates with a message to the effect that the disk is a GPT disk, then that's what it is.

I haven't researched the issue in detail, but the Ubuntu installer seems to have a bug that causes it to not provide the "install alongside" option for many computers that ship with Windows 8 pre-installed. I suspect that this is the issue you're seeing. Unfortunately, the only solution I know of is to use the "something else" option. Note that you'll almost certainly need to correctly identify your EFI System Partition (ESP) to the installer. It's a FAT32 partition, typically 100-1000MB in size, and you tell the installer to use it as an "EFI boot partition." (Why the developers chose too change "system" to "boot" is beyond me. Such changes just create confusion; but I digress....)