I have three NVMe drives formatted with ext4 and want to install Windows on a fourth, completely separate NVMe drive. How likely is a modern Windows installation to modify or damage data on the Linux drives, including their EFI system partitions? The three existing NVMe drives are installed in motherboard slots that are blocked by my GPU, so removing them temporarily would be difficult. I have used Linux for nearly 20 years but have very little experience with current Windows behavior and dual-boot setups.
4 Answers
After installation, disable Windows Fast Startup. It can leave NTFS volumes hibernated and cause problems when accessing them from Linux. This setting is less about protecting ext4 and more about avoiding filesystem and dual-boot surprises.
If all drives remain connected, carefully verify the target disk and boot mode before starting the installer. You can create or use an EFI partition on the Windows drive, then configure your existing boot manager to chain-load Windows afterward. It is not guaranteed that Windows will overwrite anything, but separate drives do not automatically prevent bootloader changes.
The safest approach is to disconnect or disable the Linux drives during the Windows installation. Windows sometimes writes its bootloader to the first EFI partition it finds, regardless of which drive receives the operating system. If physically removing the drives is impractical, disabling their controller or ports in firmware may work, depending on the motherboard.
The ext4 data itself should generally be safe because Windows does not normally use or modify ext4 volumes. The bigger risk is the EFI system partition or bootloader: Windows may place its boot files on an existing EFI partition instead of the drive you selected. Back up anything important first, and be prepared to repair or reinstall your Linux bootloader.

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