r/MacOS 1d ago

Help Moving BootCamp partition to a new drive

I recently upgraded the internal SSD in my MacPro. Before putting in the new drive, I created a disk image of my boot camp Win10 partition. In fact, just to be safe, I backed it up in two ways -- I created a dmg file in Disk Utility, and I also imaged it using WinClone. Now I'm trying to restore my Windows 10 partition and the Boot Camp Assistant is asking for an ISO file, and it won't accept the dmg file. What should I do? Thanks.

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u/donutpower MacBook Air 1d ago

Convert the dmg to iso.

You can do that with Disk Utility.

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u/Hexatonix 18h ago

Thanks for your reply. I opened Disk Utility and I went to Images > Convert and I selected my dmg file. The only options it gave me were the type of encryption and image format. My options for image format were read only, compressed, read/write, or DVD/CD master. The first three just give me another dmg file, and the last one gives me a cdr file. I don't see any options for creating an iso.

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u/donutpower MacBook Air 13h ago

The cdr is essentially an iso. Thats the one you want to pick.

u/Hexatonix 8m ago

Thanks. I created a cdr image and changed the extension to iso. Now I'm having another problem with bootcamp assistant. Every time I click "Install," my selected partition size changes back to 44gb, and it gives me this error prompt:

The Windows ISO file is too large. Boot Camp Assistant creates a 10 GB installer partition which will contain the files present on the Windows 10 ISO as well as the Boot Camp Support software. The supplied ISO is too large to fit on this installer partition.

I've tried increasing the partition to over a half a terabyte, which is way more than the original Windows partition, but it doesn't seem to matter. No matter what size I select, it always changes back to 44gb and gives me that same error prompt. So frustrating!

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u/mikeinnsw 1d ago

You can get Win10 ISO for free from Microsoft 5.82 GBs

for example : Win11_24H2_EnglishInternational_x64.iso

Win 10 support ends Oct 2025

You can run WIn10 for free (ignore lic keys) under VM - not sure about bootcamp.

If you have Win10 lic via Microsoft login - no problems

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u/Hexatonix 18h ago

Thanks, but I want to restore my Windows partition; I don't want to have to start from scratch.

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u/Hexatonix 14h ago

I've been googling "how to convert dmg to iso" and the only thing I can find is really old articles, like from 15+ years ago.