For a dual-boot Windows / Linux PC, set BIOS / UEFI to boot to the Windows hard drive, especially if using Windows BitLocker. If Windows won’t boot, the Windows HDD boot sector may need repair. Windows error 0x800703ed may occur if a dual boot system tries to start Windows from Grub instead of directly via BIOS / UEFI selection. It is best to use a separate hard drive for Windows.
Backup the PC to an external hard drive or the cloud. Create bootable Windows USB drive via Windows Media Creation Tool. Use Rufus to write the ISO to USB. Boot from USB and select a partition to install Windows on. Don’t delete Recovery partitions or you may lose your Windows OEM license.