It's been so nice to have so fewer computer issues since I switch to Mac about four years ago. Today I try to do something with Windows and it's taking a day instead of the hour or so I had in mind I want to be as detailed as I can, so I'm sorry for the super long explanation. A big thank you to anyone who'd like to read through it and might know what could be done to fix this though. Here's what I've done and what has happened: I made a bootable USB stick from a Windows 8 installer ISO. On my 2013 MacBook Air, using Boot Camp Assistant, I downloaded the Windows support files onto that same USB stick and I partitioned my Air's SSD to about 40gb for Win8. I reboot with the USB in. (I will say right now that this is the only USB/peripheral thing plugged into my Air at this time.) The Windows installer starts up and it looks okay. At the beginning of the install menus, it lists my disks/partitions, in order, as: Drive 0 Partition 1: EFI (Type) System Drive 0 Partition 2 (Type) Primary Drive 0 Partition 3 (Type) Primary Bootcamp Partition (can't recall its exact title) It tells me it can't install to my Bootcamp partition because it needs to be formatted to NTFS. Seems to be no choice, so I format it to NTFS right there in the Windows installer. I hit "next" and it seems to be installing okay. "Copying Windows files." Check "Getting files ready for installation" It always stops at 91% and gives a message: "Windows installation encountered an unexpected error. Verify that the installation sources are accessible, and restart the installation. Error code: 0C0000005" My only option is to press "Okay" and it reboots the computer. Just in case this is the USB stick's problem, I made a 20gb external HDD into a bootable Windows installer the same as I did with the USB stick, but I get the same issue. I've tried, in the Windows setup, deleting the Bootcamp partition and from that blank space I create a new partition right there. Same issue happens. THEN When I reboot my MacBook Air, I'll hold the Option key to manually choose a startup option. From here, I can select a disk called "Windows", but of course there is no Windows installed there [yet] so it brings me to the USB's install menu but in a lower resolution. The menu seems like it's the same, except Only from here will it tell me that it can't install on my partition because "the selected disk is of the GPT partition style." It really seems like there's nothing I can do. You would think that if this was normal for MacBook Air and Boot Camp, I'd be seeing tons of mentions about it when I search for a solution. But why is my Air behaving so different? I'm sorry I couldn't explain this all more succinctly. But I think it just comes down to: My Bootcamp partition is an incompatible GPT style(?). And for some reason it only tells me that when I indirectly boot from the USB drive(??). Not to say this is definitely Window's or Microsoft's fault. I don't know well enough to insightfully judge. But just ****mnit. This sort of endless labyrinthine headache is why I sold my Dell laptop four years ago and never looked back.