Installing Windows from an external USB flash stick, using Boot Camp

Discussion in 'Windows, Linux & Others on the Mac' started by laserfan, Apr 13, 2014.

  1. laserfan macrumors member

    Jul 13, 2012
    I want to help my friend install Windows 7 to his new iMac using I guess Boot Camp Assistant, but his Mac doesn't have an optical disk drive. So I have USB flash drives, and a W7.iso image (3.2Gb) that I've downloaded, but what to do with it i.e. what format do I use for the USB stick (e.g. FAT32)? Simple copy of the file to the empty USB stick? Now the .iso is on the USB stick--what next? The Boot Camp installation instructions are not at all clear as to how to do this e.g. Step 2 Prepare your Mac for Windows sub 5 says "Insert your Windows 7 installation disc into your computer's optical drive, or insert the USB flash drive with Windows 7 into a USB port on your computer" then "Click Install".

    So if my FAT32 USB stick with X17-58997.iso (W7HPx64SP1) copied to it is inserted at this point, the Mac will see it and launch the .iso somehow?

    I need help please!

    Yes I know once we get W7 loaded he has 30 days to get a Product Key but we'd like to get started right away...
  2. whiteonline macrumors 6502


    Aug 19, 2011
    California, USA
    The Windows ISO should be located on the iMac.
    The Bootcamp assistant runs the following steps:
    1. Automatically format the USB stick and extract the ISO to it.
    2. Automatically copy the Bootcamp drivers to the USB stick.
    3. If selected to install, you will repartition the iMac hard disk to make room for the Windows installation.

    Once done, reboot and you will begin the Windows setup.
  3. laserfan thread starter macrumors member

    Jul 13, 2012
    Thanks a lot--my addled brain was missing what now appears obvious--to copy the ISO to the iMac first. And I should know that iMacs can read USB sticks with other formats. At least, when I installed OSX to a virtual machine on my PC awhile back the Mac OS had no trouble reading my USB sticks..

    So I'll copy the .iso from the USB stick first, and then let BC have its way with it.

    Thanks again. :)
  4. Quackers macrumors 6502a

    Sep 18, 2013
    Manchester, UK
    Bootcamp Assistant will copy the iso to the USB stick if you point it to your Windows.iso file.
  5. laserfan thread starter macrumors member

    Jul 13, 2012
    Hmm I suppose if my USB stick with the W7.iso, and a second USB stick to be built by BC for booting can be inserted both at the same time, then I might save the step of copying my .iso to the iMac first. Slow I suppose, USB-in-to-iMac-out-to-2nd-USB...
  6. laserfan thread starter macrumors member

    Jul 13, 2012
    I nominate YOU to write Apple's docs for them whiteonline! This process is much simpler than their obtuse documentation suggests!

    I did just plug my USB stick with W7.iso on it, together with another USB stick to make the WININSTALL, and it copied-across w/o issue.

    What WAS an issue however was that Step 2, which involves Downloading the latest Bootcamp software, was taking forever so we aborted it. Turns out this download is a GB in size, and my friend's ISP was not up to it today. He is going to probably re-start it when he goes to bed tonight.

    With my previous ISP it would not have even been possible to download this; I was limited to 200Mb per day and then it would kick me down to modem speeds.

    And Apple's docs don't even mention the download much less the potential for "forever". :apple:
  7. Gjwilly macrumors 68030

    May 1, 2011
    SF Bay Area
    So if I've already got a bootable Windows 7 installation flash stick can I use that or do I still have to have to put the .ISO on the Mac and let Boot Camp create a new flash stick?
    Seems like an unnecessary step.
  8. laserfan thread starter macrumors member

    Jul 13, 2012
    AFAICT Boot Camp Assistant would normally extract the .iso to a flash stick that it re-writes, then adds the Boot Camp Software (drivers) to that stick.

    In your case you might try separately downloading the correct Boot Camp Software for your Mac, and extracting its .zip contents to your W7 flash stick, and then in BCA skipping (unchecking) those two steps, going straight into creation of the partition.

    Worth a shot IMO, especially as I've read elsewhere here that BCA sometimes has trouble making a bootable disc.

    EDIT: actually it's called Boot Camp Support Software:

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