How to fix "doesn't look like an EFI partition" with WinUSB?

Using WinUSB I get this error. I would appreciate any help as I'm trying to put Windows back on computer to please th' wifey, then dual boot so i can still use Ubuntu.

Installation failed !
Exit code: 512
Log:
Formating device...
Mounting...
mount: block device /home/lighthouse/Downloads/Windows 8.1 Update 1 Pro X64 PreActivated/Windows 8.1 Update 1 Pro X64 PreActivated.iso is write-protected, mounting read-only
Copying...
Installing grub...
Installing for x86_64-efi platform.
grub-install: error: /media/winusb_target_1412439366_7311 doesn't look like an EFI partition.
.
Error occured !
Syncing...
/usr/bin/winusb: line 78: 15592 Terminated while true; do sleep 0.05; echo 'pulse';
done
Cleaning...
/usr/bin/winusb: line 78: 15971 Terminated while true; do sleep 0.05; echo 'pulse';
done
Umounting and removing '/media/winusb_iso_1412439366_7311'...
Umounting and removing '/media/winusb_target_1412439366_7311'...

2 Answers

If what you want is to create a bootable usb to install Windows 8, you must use the dd command in Ubuntu:

Open a terminal.

Run it:

dd if=/path/to/file.iso of=/dev/sdb

Note: Carefully check that the usb-stick is /dev/sdb

That really depends on what type of bootable USB you want to make. If you want to make a classic MBR, BIOS bootable Windows USB try this solution.

If you want to make a USB to install Windows in UEFI mode, things are different:

1. Apply a GPT partition table to the USB drive and format it as FAT32 using GParted
2. Copy Windows files from DVD/ISO to USB using the file manager
3. Look for a bootx64.efi file in efi/boot folder in USB drive. If it doesn't exist extract it from the Windows ISO, sources/install.wim file by opening it with 7z unarchiver. You can find a bootmgfw.efi file in ./1/Windows/Boot/EFI. Extract it, rename it to bootx64.efi and place it on USB in efi/boot folder.

Now the USB drive is UEFI bootable (but not BIOS) and can be used to install Windows in EFI mode. The complete guide is available on my website both for BIOS and UEFI.