Get a Windows machine to boot again after GRUB broken, Linux and Ext4 partitions erased

Create a windows recovery drive on a usb using the Windows Media Creation Tool. You should not need to format the USB, as it will do this for you. Use the boot menu or BIOS/UEFI to boot from the usb. Once the utility has loaded, select to repair your computer with command prompt. In the command window that appears type bootrec.exe /fixmbr and press [Enter]. Exit the command window and power down the computer. Unplug the USB and attempt to boot.