So I had a functional triple boot system with OSX, Win 8 x64 EFI and now x64 Linux Mint on four usable partitions on a retina Macbook Pro. Windows 8 had a minor "windows update" problem that in trying to solve broke my machine so it would only safeboot. Then system refresh and/or automatic repair destroyed it to the point that even a system reset is impossible. Certainly the restore points are gone. Currently I cannot reinstall Windows. Somewhere in the above Windows devolution I believe that the GPT got damaged. I would like to attempt a repair on that partition before I wipe the disk and start over. I was hoping for some advice from any GPT experts. Here is what I know... from MacOS $ gdisk /dev/disk0 p Disk /dev/disk0: 490234752 sectors, 233.8 GiB Disk identifier (GUID): ... Partition table holds up to 128 entries First usable sector is 34, last usable sector is 490234718 Total free space is 936829 sectors (457.4 MiB) Number Start (sector) End (sector) Size Code Name (my notes) 2 409640 146894007 69.8 GiB AF00 Customer (OSX created HFS Plus) 3 146894008 148163543 619.9 MiB AB00 Recovery HD (OSX created) 4 148164608 148426751 128.0 MiB AF00 Apple_HFS_Untitled_2 (unknown) 5 148426752 148688895 128.0 MiB 0C01 Microsoft reserved par (unknown) 6 148688896 343736319 93.0 GiB 0700 Basic data partition (Win created NTFS) 7 343738184 382800679 18.6 GiB 0700 DOS_FAT_32_Untitled_3 (Linux 3.5 created ext3) 8 383062824 489972567 51.0 GiB 0700 Windows_NTFS_Untitled_ (Win created exFAT) You can see my notes on the far right (my notes in parenthesis) that some of the listed partition types are incorrect. From Windows 8 x64 EFI install I see these partitions Name Total Size Type Drive 0 Partition 1 200 MB Primary Drive 0 Partition 2 69.8 GB System Drive 0 Partition 3 619 MB Primary Drive 0 Partition 4 128 MB Primary Unallocated Space 163 GB In selecting the "unallocated space" (which I realize is wrong) from the partition selection screen I get these three errors in the from partition 4 above Windows cannot be installed to this hard disk space. The selected disk has the maximum number of partitions of this type. Windows cannot be installed to this disk the selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks Windows cannot be installed to this disk This computer's hardware may not support booting to this disk. Ensure that the disk's controller is enabled in the computer's BIOS menu From the Win 8 x64 EFI command prompt under "diskpart" I get only the first four partitions. I can't even find diskpart.efi from the install disk. Advice? I was thinking about trying the following manually changing the partition types in gdisk trying to find and run window's diskpart.efi removing the MBR and/or rebuilding the MBR trying any MBR sync utilities from rEFInd trying clean or repair functions from gdisk trying clean or repair functions from EaseUS Partition Manager The Linux partition couldn't be the culprit. I don't think Linux bootloads in EFI, but the Windows problems were all concluded before Linux was installed.