I get the same error, but I'm using a 64bit only Windows 8.1 ISO and different target hardware. I haven't found a workaround anywhere. I'm trying to install Windows 8.1 on a new iMac 5k* using the Bootcamp Assistant Version 5.1.2 (497) included with Yosemite 10.10.1. I bought Windows 8.1 on a Windows 7 PC and used Microft's mediacreationtool.exe utility to create the 64-bit-ONLY iso. The utility allows you to select the Edition of Windows 8.1 (vs 8.1 Pro), the language, the architecture (32bit x86 or 64 bit x64), then you can select the media type: bootable USB or ISO.
i Selected the English 8.1 64bit ISO and copied it over the LAN to the iMac since it doesn't come with an optical drive.I launched Bootcamp Assistant and che ked all 3 available Checkboxes as described in the instructions, browsed to the ISO image, selected the FAT32 formatted USB stick and clicked continue, that's when I get the error about 64 bit Windows is required, the same as the title of Bill W's post above.
I Created the ISO again just to make sure 64 bit was selected and got the same results. I Rebooted, same result. Others said they just copied the ISO to their documents directory and that fixed it, not for me. Others said they just had to rename the ISO to DMG, that didn't work for me either.
In another article here, someone suggested modifying the info.plist for Bootcamp Assistant, I tried that, same result as several others, problems with unlocking and replacing the edited .plist file.
When I examine the files in the ISO on the PC, there's nothing to indicate that there are two builds to support both Windows architectures. Other people claim they've installed Win 8.1 on this hardware successfully using the same technique.
Any ideas? Any additional info required?
Thanks in advance! Is there a way to cross-post this in other forums or threads if this is not the best place for it?
Matt
*My iMac is close to its factory state (I some App Store apps), iMac (Retina 5K, 27", late 2014, Model ID 15,1), Yosemite 10.10.1 (Build 14B25), i7, 3Tb Fusion, 32Gb RAM, 295M w/ 4G, SanDisk Cruzer Edge Media brand USB memory stick with 16Gb for use with Bootcamp. 1Tb free space on Fusion drive, was planning to allocate 100Gb out of that for Windows.
