Mount the installation ISO. # mount -o loop winstall.iso /mnt/iso
Mount the USB drive. # mount /dev/sdX1 /mnt/usb
Copy over files (-a for archive mode, -v for verbose). # cp -av /mnt/iso/* /mnt/usb/
Unmount everything. # umount /mnt/usb /mnt/iso
This is where it gets a bit strange. Windows uses the disk MBR to load the partition EBR for boot, so we must prepare both.
Prepare the partition EBR. # ms-sys -n /dev/sdX1
Prepare the disk MBR. # ms-sys -7 /dev/sdX
Wait for the buffer cache to flush. # sync
Reboot into the USB drive.
The installer won’t proceed after I select a disk with the error “we couldn’t create a new partition or locate an existing one”. I had to unplug my primary Linux HDD’s SATA cable so that the Windows drive was the only one.