I have problems with a windows game on Bootcamp that used to work fine, and now doesn't. So I tried making a bootable bootcamp on a USB. Bootcamp runs on the USB but I would say it doesn't run as well as on my mac's internal HDD. Windows tend to not respond a lot. Also, the 32bit windows game on the USB crashes from memory errors even though I use LargeAddressAware. The game does not crash on my original bootcamp and I can get the game to use over 2GB RAM and it doesn't crash. I think maybe getting my original bootcamp setup on the flash drive might fix my issue. I also want to use this USB to be able to test doing things without it messing up my original bootcamp.

I have read that bootcamp can have problems from USB and it's better to clone your existing bootcamp to the USB. Using WintoUSB seems like a great option, but I have Windows 10 Pro, and you can't use WintoUSB with Windows 10 Pro.

I have also read that you can create a .CDR image using Disk Utility and then convert it to an .iso; then I guess I can use Rufus maybe to burn it to the usb. But the problem is, the BOOTCAMP uses 100GB but is a 230GB partition. I have more than 100GB available on my mac, but not 230GB and it told me there's not enough space. Also, everything I try takes so long, so I want to know what will work because I'm getting nowhere when trying things myself.

Can anyone suggest an easy way to clone BOOTCAMP (with Windows 10 Pro) to a USB? I have access to both Mac and Windows to do this from. Ideally I want it to clone directly so I don't have to store the 100GB or 230GB somewhere other than the USB drive.

  • I seem to recall there was (is?) a utility called Winclone that could clone/backup your Boot Camp partition and then restore it elsewhere, if needed. Sounds like it might do the trick. Certainly easier than mucking about in the command line with "dd." Commented Mar 2, 2023 at 16:14
  • Unfortunately Winclone requires me to buy a licence before I can clone the partition to a winclone image. I'm looking for a free solution. Commented Mar 2, 2023 at 17:33
  • Microsoft themselves abandoned Win2Go, even for previously fully-supported hardware. Without it, Windows is very hard to persuade to boot from any external drive. Add to that, that it runs very poorly even from external SSD; from USB stick it's going to make molasses look fast. I don't think it's worth the effort at all.
    – Tetsujin
    Commented Mar 2, 2023 at 18:55
  • You want clone Windows, which used to work fine but now doesn't, to a flash drive. If the problem is software related, then you should expect the same problem with the clone. If the problem is hardware related, you should expect the same problem, unless maybe if the problem is a defective HDD. Commented Mar 2, 2023 at 23:01
  • @DavidAnderson Yes, I am suspecting the HDD. Crystal disk says there are 25 reallocated sectors. I don't see why this would cause a problem, but it made me wonder. I also wondered if the faster read/write speeds would help run the game. Commented Mar 3, 2023 at 23:33

1 Answer 1


Since you feel your internal HDD is failing, you would be better off doing a clean install of Windows 10 to a bootable external SSD. I would not recommend trying to install Windows to flash drive. The Boot Camp Assistant can not be used to install Windows 10 on to a external SSD. There are references given at the end of this answer, which outline various methods that can be used to install Windows 10 to an external USB SSD.

Currently, you have Windows 10 install on your internal SATA HDD. The SATA interface has a maximum transfer limit of 6 Gb/s. This is more than adequate of HDDs, which generally have a transfer limit that does not exceed 3 Gb/s. Modern SSD chips can read/write data a speeds which well exceed 10 Gb/s. This means the performance of a Windows 10 installation on a modern external SSD should exceed that of your existing internal SATA HDD installation. The table below shows which ports on your Mac you can connect an external SSD.

Name Port Type Transfer Limit Does Transfer Limit Have
a Major Effect on the
External SSD Speed?
USB 3.2 Gen 1x1
USB 3.2 Gen 1
USB 3.1 Gen 1
USB 3.0
USB Type A 5 Gb/s Yes
USB 3.2 Gen 2x1
USB 3.2 Gen 2
USB 3.1 Gen 2
USB Type C 10 Gb/s Yes
Thunderbolt 3 USB Type C 40 Gb/s No

You should expect an external SSD which has a higher transfer limit to cost more and perform better than external SSDs with a lower transfer limit.

Windows 10 is scheduled for retirement on Oct 14, 2025. You might consider installing Windows 11 on an external SSD. I did this late last year and was able to upgrade from Windows 10 for free. I do not know is upgrading is still free.


  • Thank you. This is really helpful. I don't have an external SSD but have just ordered one. Commented Mar 4, 2023 at 17:40

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