Blank screen with white underscore when trying to install Windows

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Level 1

5 points

Blank screen with white underscore when trying to install Windows

I am attempting to install Windows 8.1 onto a 21.5-inch Mid 2011 iMac using a Windows 8.1 DVD.

I use BCA to create the partition and setup the tools, however when the Mac restarts the system displays a blank screen followed by a blank screen with a flashing underscore and then sits there entirely idle no matter how long I leave it.

It begins to read the DVD and then just stops.

I have tried the following.

Tried re-creating the BCA partition multiple times.
I'm selecting "Windows" DVD manually from the boot option menu.
Tried different Windows Install DVDs.
Attempted to install from USB (but this only seems to support a real EFI install).
Tried using an external DVD drive for the install (this has the same behaviour however it ejects the disc after a minute).

I'm not sure what other steps to try, is anyone able to offer any advice?

I previously installed Windows 7 without any issue on this Mac.

Thanks

iMac (21.5-inch Mid 2011), OS X Yosemite (10.10.4)

Posted on Aug 4, 2015 12:59 AM

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Answer 1

Best reply

Loner T

Level 9

59,471 points

Aug 4, 2015 5:21 AM in response to NewDigger

There are several possible issues.

1. If the DVD was manually created and has block errors, or the source ISO is corrupted, which results in an unreadable DVD. It may still work properly in Finder and show file content. The ISO source, if used, should be verified with the source using a MD5sum or SHA1 checksum.

2. You may have external storage devices or hubs connected to your iMac. They should be disconnected during the Windows installation.

3. If you are using a DVD, there is no need to manually interrupt the Windows installation. The NVRAM settings created by BCA are used by the Apple Bootmanager to continue the installation. Your Mac is a preUEFI Mac, so no EFI boot support.

4. External Optical drives are not supported for Windows installation on Macs which come with built-in Optical drives. This is also used by BCA to configure the NVRAM. If you have a failed installation, you should

Resetting the System Management Controller (SMC) on your Mac - Apple Support

How to Reset NVRAM on your Mac - Apple Support

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Answer 2

NewDigger Author

Level 1

5 points

Aug 4, 2015 5:36 AM in response to Loner T

Hi Loner T

I will check the ISO checksum. The DVDs which were created were verified by Disk Utility after creation. (I have used that ISO to create a working Virtual Machine though).
I have removed all external hardware so that no USB ports are in use.
I'll leave BCA to its own devices.
I'll make sure to use the built-in optical drive.
I have attempted to reset the SMC already and will do a NVRAM reset when I am next at the machine.

Thanks for the suggestions. I will let you know the results.

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