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Windows To Go on 2014 Macbook Air

E

eddjedi

macrumors 6502a
Original poster
Sep 7, 2011
642
880
I've spent the last couple of days trying to get this working without success. As I have an SSD in my Macbook Air space is at a premium, and I don't want to waste it on a Windows partition I'll only occasionally use. So I've bought a decent quality Sandisk 64GB USB 3.0 drive that I want to install Windows to go on. I've found dozens of conflicting guides and opinions on the matter, but still no joy getting it working so was hoping somebody here can help. So far I've tried:

Windows 8.1 To Go - won't boot at all. I've read conflicting reports that Windows 8.1 will or won't boot from a 'removable' USB drive.

Windows 8 To Go - works fine on a MBP 2012 I have at my office, but refuses to boot on my MBA. It gets to the Windows logo/loading icon, but then shows a blue screen saying there's a problem and it reboots.

I have tried all the various online tips such as installing the Bootcamp drivers via dism, even creating a 'hidden' EFI partition etc, but can't get anything to work.

The only thing I can get to 'boot' on my MBA is a Windows 8.1 installer I made using Bootcamp, so it looks like the MBA can indeed boot Windows, but this particular method is no use as you can't install on a removable drive from the Bootcamp installer.

Can anybody put me out of my misery? Or confirm it works on their MBA so I don't give up all hope?
 
I only have 4GB RAM so I don't think it will run very well. Also I don't really want to use ANY of my SSD storage on Windows, whether it's a partition or VM image.
 
eddjedi said:
I only have 4GB RAM so I don't think it will run very well. Also I don't really want to use ANY of my SSD storage on Windows, whether it's a partition or VM image.
Click to expand...

You can run your vmware off an external drive. What apps are you looking to run. The ram constraint may not be a major issue.
 
I guess a VM on the external USB is a fallback option, but I'd much rather have a 'native' Windows installation available, just not on a Bootcamp partition. If it can't be done I'm happy to accept it, but I've seen dozens of posts claiming it can and as said have it running perfectly on an older MBP. There seems to be something about the MBA it doesn't like.
 
eddjedi said:
I guess a VM on the external USB is a fallback option, but I'd much rather have a 'native' Windows installation available, just not on a Bootcamp partition. If it can't be done I'm happy to accept it, but I've seen dozens of posts claiming it can and as said have it running perfectly on an older MBP. There seems to be something about the MBA it doesn't like.
Click to expand...

Windows to Go UEFI

Connect external drive to Windows VM. You must have a Windows VM in VMware/Parallels/VBox, or a Windows PC. Any existing Windows environment will do.

What you need:
install.wim file (obtain this from your Windows ISO)

Open elevated cmd.exe (run as admin)

Note: All commands aren't case sensitive, including pathway to files.

Type diskpart
Type list disk
Take note of the disk you want to select
Type select disk 1 (if your disk is Disk 1)
Type clean
Type convert gpt
Type create partition EFI size=100
Type format quick fs=fat32 label=EFI
Type assign letter=S
Type create partition primary
Type format fs=ntfs quick label=W2G (or any other name you wish for label)
Type assign letter=E
Type exit

Open up File Explorer. In your C drive, create a new folder named WIN2GO.
Put the install.wim file in this folder

Back in cmd.exe:
Type dism /apply-image /imagefile:C:\WIN2GO\install.wim /index:1 /applydir:E:\ (this process will take quite a while)
Type E:\Windows\System32\bcdboot E:\Windows /s S: /f UEFI

Restart your entire Mac. After the chime, hold down Option and when prompted to select your boot drive, select EFI Boot.

Proceed installation normally.

After installation, install Boot Camp drivers. Feel free to trash the VM once you're done too.

For best results, use USB 3/Thunderbolt. If you don't have USB 3, use Thunderbolt. If you have neither, stick back to the internal drive :)

This method works on all my Macs, be it the ones that use the older EFI (Ivy Bridge and earlier), or the ones that use the new UEFI (Haswell and later).
 
I just tried your method to double-check and got the following error when trying to execute format quick fs=fat32 label=EFI:

"This operation is not supported on removable media"

Have you tried your method on USB flash drives, or just external hard drives?
 
Here's what I'm getting while trying to boot.
 

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And another with the error message, looks like it may be a read/write error issue? Could that be a problem with the USB drive itself or the MBA? I've also now tried booting it on a PC laptop (Lenovo Thinkpad) and it also boots fine, so this seems to be an issue specific to the Macbook Air rather than an issue with the USB stick or the installation.
 

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Last edited:
eddjedi said:
I just tried your method to double-check and got the following error when trying to execute format quick fs=fat32 label=EFI:

"This operation is not supported on removable media"

Have you tried your method on USB flash drives, or just external hard drives?
Click to expand...

External USB 3 hard drive.

The problem is with your USB itself, which probably doesn't support the new UEFI 2.0 standard used in the Haswell Macs, like your MB Air.

Older MacBooks like the 2012 ones use the older EFI 1.1.

The best way is to use an external hard drive (preferably with UASP support).
 
Thanks, that would explain it. So can anybody recommend a USB flash drive that does support UEFI 2.0? I'd rather not have to connect to an external HD as even the small ones aren't really portable or happy to move around much.
 
Have you considered an mSATA external SSD?

About 1/3 of the size of a 2.5" external and capable of housing up to a 1 TB SSD.

I have one with a 120 GB Crucial drive in it and bought it for $115 including the case.

http://www.amazon.com/gp/aw/d/B00LRZPNHM

B
 
eddjedi said:
Thanks, that would explain it. So can anybody recommend a USB flash drive that does support UEFI 2.0? I'd rather not have to connect to an external HD as even the small ones aren't really portable or happy to move around much.
Click to expand...

I'd not use any form of USB sticks at all, since the cheap flash memory used in USB sticks isn't meant for high speed I/O operations incurred when running an entire OS off it. You'll be dooming the pen drive's flash memory that way, because it can't sustain the amount of reads and writes involved. External SSDs will last hundreds of times longer.

Any USB sticks are out of the question, because of performance and reliability issues.
 
yjchua95 said:
I'd not use any form of USB sticks at all, since the cheap flash memory used in USB sticks isn't meant for high speed I/O operations incurred when running an entire OS off it. You'll be dooming the pen drive's flash memory that way, because it can't sustain the amount of reads and writes involved. External SSDs will last hundreds of times longer.

Any USB sticks are out of the question, because of performance and reliability issues.
Click to expand...

I would agree with you about the $5 USB sticks you buy from Chinese eBay, but the whole point of Windows to Go is that it will run properly on "Certified" USB flash drives, eg:

http://www.kingston.com/en/usb/bootable

I think the SanDisk USB 3.0 one I have would be up to it.

So one thing I can't get my head around is that the USB stick I have WILL boot the Windows 8.1 installer created on my Mac. However it won't boot the one made on a Windows PC. So that indicates to me that it must be possible to 'force' the Mac to boot from this USB stick.
 
eddjedi said:
I would agree with you about the $5 USB sticks you buy from Chinese eBay, but the whole point of Windows to Go is that it will run properly on "Certified" USB flash drives, eg:

http://www.kingston.com/en/usb/bootable

I think the SanDisk USB 3.0 one I have would be up to it.

So one thing I can't get my head around is that the USB stick I have WILL boot the Windows 8.1 installer created on my Mac. However it won't boot the one made on a Windows PC. So that indicates to me that it must be possible to 'force' the Mac to boot from this USB stick.
Click to expand...

Actually, there is no installer involved.

What my instructions actually do is to install Windows directly into the external device, so that when you first start up from it, it will directly go to the Personalize screen.

I tested my own Kingston HyperX 1TB stick (I know, it's a massive one, but I use it when deploying software in clients' systems), and it booted in UEFI on Macs and PCs just fine.

That said, it wouldn't boot from a PC that had an older motherboard. It would only startup on PCs with UEFI-compliant motherboards.
 
Sorry installer was the wrong word, what I meant was a full installation as you pointed out.

One difference I can see is that the bootable Windows 8.1 installer created with Bootcamp is formatted as fat32. But the "installed" Windows bootable package is formatted NTFS.

I still can't understand the issue here. If it didn't boot at all then fine, but it clearly can boot and read from the USB as it gets to the Windows logo.
 
eddjedi said:
Sorry installer was the wrong word, what I meant was a full installation as you pointed out.

One difference I can see is that the bootable Windows 8.1 installer created with Bootcamp is formatted as fat32. But the "installed" Windows bootable package is formatted NTFS.

I still can't understand the issue here. If it didn't boot at all then fine, but it clearly can boot and read from the USB as it gets to the Windows logo.
Click to expand...

I forgot.

When OS X formats the USB stick as FAT32, it actually creates a hybrid MBR partition table. This means that OS X sees it as GPT and Windows sees it as MBR.

In order to install Windows UEFI on it, you have to first use gdisk to turn it back to a pure GPT: http://superuser.com/questions/508026/windows-detects-gpt-disk-as-mbr-in-efi-boot

Then only you will be able to install Windows UEFI on that stick and get all the way to the setup screen.

EDIT: I just reviewed my own steps, the steps actually included the part to convert the whole stick to GPT from within cmd.exe, so the gdisk thing is unnecessary.

The issue is that your USB stick probably doesn't support UASP.
 
I tried using the tool mentioned above to format as GPT:

https://rufus.akeo.ie/

But although I could then mount the drive in OS X, it did not show up at the boot screen at all. Will try using the tool you mention instead.
 
eddjedi said:
I tried using the tool mentioned above to format as GPT:

https://rufus.akeo.ie/

But although I could then mount the drive in OS X, it did not show up at the boot screen at all. Will try using the tool you mention instead.
Click to expand...

On a side note, my method worked for someone else, although not on all drives: https://forums.macrumors.com/threads/1829989/

I'll be testing my method again on several other drives, and will post back with results.

Keep in mind that my method will only work on Macs and not all PCs. Only PCs with UEFI motherboards will work.
 
UPDATE: It works!

I thought I'd give Windows 10 (Enterprise N) a whirl, and sure enough it works! not sure what exactly my MBA didn't like about Win 8.1, but 10 seems to be working just fine. I used this program to install Windows to my USB flash drive:

http://www.easyuefi.com/wintousb/
 
eddjedi said:
UPDATE: It works!

I thought I'd give Windows 10 (Enterprise N) a whirl, and sure enough it works! not sure what exactly my MBA didn't like about Win 8.1, but 10 seems to be working just fine. I used this program to install Windows to my USB flash drive:

http://www.easyuefi.com/wintousb/
Click to expand...

Hello eddjedi thx for the generous sharing. I'm using a Sandisk Extreme USB 3.0 flash drive 64GB. I've tried many ways to install Windows 10 (Enterprise/Pro) on the UFD trying to boot and run on an MBA (2015) but failed.:((( I also tried WintoUSB. When coming to the screen of selecting destination disk, I selected the UFD (already partitioned to 100MB FAT32 and 59GB NTFS using third party partition tool). However, WintoUSB always repartitioned the UFD to a single NTFS partition, which could not be booted on the MBA.

You said "It works!" Did you mean it works on your UFD (and not SSD)? If so, could you please tell me the details? Thank you very much!
 
Yes on a USB 3.0 Sandisk flash drive, not an SSD. No special instructions, pre-formatting etc, wintousb took care of the whole process.

EDIT - I do remember selecting the 'legacy' option, try that.
 
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