Although Windows 7 is long out of support, a friend asked me to assist in recovering his laptop OS, so I put aside my preferences and prejudices to see what I could do to help.

I found many sets of instructions about how to make a bootable USB after copying across the contents of the ISO. However, even the tools that were Linux based were not readily installed on a modern distribution.

I finally realised that Grub was all I required, and the following is a walk-through of the steps taken.

USB Drive Configuration

The drive needs to have sufficient capacity to hold the contents of the Windows 7 ISO (about 8 GiB).

Replace sdX below with the device associated with the USB drive.

Format

The first step is to format the USB drive. The drive is formatted with an MSDOS partition table, with a single NTFS formatted partition. The label for the NTFS partition is W7SP1PRO64 (this will be used later).

Partition USB:

$ sudo sfdisk -d /dev/sdX <<EOF
label: dos

size=7.5GiB, type=7
EOF

Format partiton:

$ sudo mkfs.ntfs --fast -L W7SP1PRO64 /dev/sdX1

Copy ISO Content

Mount the ISO image to copy from (replace win7.iso with the name of your ISO file):

$ sudo mount -r -o X-mount.mkdir win7.iso /tmp/win7-iso

Mount the USB partition to copy to:

$ sudo mount -o X-mount.mkdir /dev/sdX1 /tmp/win7-usb

Copy ISO contents to USB:

$ sudo cp -v -r /tmp/win7-iso/* /tmp/win7-usb
$ sync

The sync may take a long time, dependent on the speed of your USB port and driver.

Make USB Bootable

Install Grub onto the USB drive:

sudo grub-install \
  --target=i386-pc \
  --install-modules="normal search ntfs ntldr" \
  --locales=uk \
  --boot-directory=/tmp/win7-usb \
  /dev/sdX

Create the file /tmp/win7-usb/grub/grub.cfg (the label must match the label of the NTFS filesystem created above):

insmod ntfs
search --no-floppy --label W7SP1PRO64 --set root
ntldr /bootmgr
boot

Conclusion

Unmount all of the drives, and arrange to boot from the USB drive. If all has gone well, you’ll see the Windows 7 installer.