EDIT: I gave in and burned the DVD from a windows PC and I was able to install Windows on my MacBook Pro with Bootcamp. Sorry, that I don't have a satisfying solution.

My goal is to install Windows 7 (32-bit) on my MacBook Pro (late 2007) with Boot Camp. (I'm trying to do all this on Mountain Lion.) I am running into multiple problems creating the disk image for Windows 7. I have an ISO file of the Windows 7 DVD. I am fairly certain, that the ISO image is not corrupted. I downloaded it twice, with the DreamSpark download manager, with the same results.

Initially I tried to create a bootable USB key. The USB key is formatted as Mac OS Extended (HFS+). I opened Disk Utility, went to the restore tab, chose the ISO as source and the USB key as destination. The following errors occurred:

  • When the ISO-image is unmounted: "RESTORE FAILURE Could not validate source - Invalid argument"
  • When the ISO-image is mounted: "RESTORE FAILURE Could not validate source - error 254"

After repeating this a dozen times, I tried solve the problem from the Terminal as suggested in many forums:

$ sudo asr restore -noverify -source /path/to/windows/windows_7.iso -target /Volumes/Untitled/ -erase
    Validating target...done
    Validating source...
Could not validate source - Invalid argument

Since this also didn't work, I then tried to burn the image on a DVD. So I went into disk utility, chose the Windows 7 ISO, and chose burn.

I get prompted

Waiting for a disc to be inserted…

I insert a brand new DVD-R.The drive starts to do something and notifies me

Waiting for the drive.

And then immediately ejects the disk again and prompts me for the a disc.


3 Answers 3


The built-in Boot Camp Assistant can create a USB drive if you give it the ISO.

  • 1
    it does not even offer that
    – DataGreed
    Commented May 22, 2015 at 11:53

Try using dd instead of asr.

  1. Use mount to determine the device path of your attached USB disk. Find the disk itself and ignore the individual partition numbers. EG: if you get /dev/sda1 just use /dev/sda for the next steps.
  2. Unmount the disk in the Finder.
  3. Construct and run your dd command as such: dd if=/path/to/windows7.iso of=/path/to/usb/device
  • Note that you need to unmount rather than eject the disk. You can do this from disk utility, right clicking on the partition.
    – tog22
    Commented Apr 11, 2014 at 10:27

You can never use a mac formatted USB for Windows Use. This guide should help you burning a disc. http://lifehacker.com/251758/mac-tip--how-to-burn-an-iso-or-dmg-file-to-disc. Remember to insert a blank DVD (DVD+R recommended) and make sure it's blank before attempting to burn the ISO. If a message pops up about a blank disc, click do nothing or ignore it.

  • Answers on Ask Different need to be more than just a link. It's okay to include a link, but please summarize or excerpt it in the answer. The idea is to make the answer stand alone.
    – nohillside
    Commented Jul 27, 2013 at 14:58

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