Windows Doesn't Boot on M.2 SSD (WD_BLACK SN7702TB) Anymore

Windows fails to boot from a WD_BLACK M.2 SSD after adding a second drive because the system firmware’s boot priority has shifted or the EFI System Partition on the primary drive is no longer recognized as the active startup device. This common conflict occurs when dual-boot installations overwrite the default bootloader sequence, forcing the motherboard to attempt initialization from the new Ubuntu disk instead of the existing Windows partition.

Understanding the Boot Priority Conflict

When you install a second operating system like Ubuntu Server on a separate NVMe drive, the installation process often modifies the UEFI NVRAM settings. The GRUB bootloader installed by Linux may register itself as the first option in the boot order, or it may remove the entry for the Windows Boot Manager. Consequently, your computer attempts to load the secondary drive, which lacks the necessary Windows recovery environment, resulting in a "No Bootable Device" error or a direct drop into a shell. This behavior is not a hardware failure but rather a configuration misalignment within the firmware layer that dictates which storage controller initializes first during the Power-On Self-Test (POST). To resolve this, you must access the BIOS/UEFI interface and restore the correct hierarchy. Enter the setup utility by pressing Del, F2, or F12 immediately after powering on the machine. Navigate to the Boot section and locate the Boot Option Priorities. Ensure that the entry labeled "Windows Boot Manager" associated with the WD_BLACK SN770 2TB drive is set as the first choice. If the Windows entry is missing entirely, you will need to manually add it using the Add Boot Option feature, pointing it to the \EFI\Microsoft\Boot\bootmgfw.efi file located on the primary drive’s EFI partition.

Verifying EFI Partition Integrity

Sometimes the issue persists even after adjusting boot order because the EFI System Partition (ESP) on the primary drive has become corrupted or inactive. The ESP contains critical files required to hand off control to the Windows kernel. If the partition flag indicating it is "active" was cleared during the Linux installation, the motherboard will ignore it regardless of priority settings. You can verify this state by booting into a Windows Recovery Environment or using a bootable USB installer. Open the Command Prompt and execute diskpart, then run list vol to identify the small FAT32 partition typically sized between 100MB and 500MB. Select this volume and assign it a drive letter temporarily using assign letter=S. Once assigned, navigate to S:\EFI\Microsoft\Boot and check for the existence of bootmgfw.efi. If these files are present but the drive still won’t boot, the partition metadata might be flawed. In such cases, repairing the boot sector is necessary. Return to the command prompt and use bcdboot C:\Windows /s S: /f UEFI, replacing C: with your actual Windows system partition letter if different. This command rebuilds the boot configuration data store and ensures the EFI partition is correctly marked for UEFI startup. For users experiencing complex multi-disk conflicts, reviewing guides on external disk booting can provide additional context on how firmware handles multiple NVMe controllers.

Managing Dual-Drive Interference

If software repairs fail to restore functionality, the interference may stem from physical controller mapping issues. Some motherboards struggle to maintain consistent device enumeration when two high-speed NVMe drives are present, especially if they are on different PCIe lanes or chipset connections. A reliable diagnostic step is to physically disconnect the WD WDS250G2B0A Ubuntu drive while keeping only the Windows SSD connected. Restart the system; if Windows boots successfully, the hardware is functional, and the problem is strictly logical. Reconnect the Ubuntu drive afterward and enter the BIOS again to ensure the SATA/NVMe mode settings remain consistent, typically set to AHCI or RAID depending on your specific chipset requirements. It is also prudent to update the motherboard BIOS to the latest version available from the manufacturer’s website. Older firmware versions often contain bugs related to NVMe hot-plugging and multi-drive boot sequences that have been resolved in subsequent releases. After updating, reset the BIOS settings to defaults to clear any residual corruption before reapplying your preferred configurations. If you find yourself stuck in a recovery loop after attempting these fixes, consult resources on resolving Windows 10 stuck in recovery mode boot loops to understand how to safely exit diagnostic states.

Preventing Future Boot Conflicts

To avoid recurrence, consider isolating the EFI partitions more clearly. While modern UEFI implementations handle multiple ESPs gracefully, keeping the Windows bootloader strictly tied to its own drive reduces ambiguity. When installing future Linux distributions, choose the option to install alongside existing OSes carefully, ensuring it does not overwrite the Microsoft bootloader directory. Additionally, regularly back up your BCD store using bcdedit /export C:\bcdbackup allows for quick restoration if the configuration becomes unrecognizable. Proper cable management and driver updates for storage controllers also contribute to stable multi-drive environments.

Frequently Asked Questions

Why does my PC say "No Bootable Device" after installing Linux?

The Linux installation likely overwrote the primary boot entry in the UEFI NVRAM or changed the boot priority order. Your motherboard now tries to start from the Ubuntu drive, which cannot launch Windows without manual intervention in the firmware settings.

Can I fix this without losing my Windows data?

Yes, modifying boot priorities and repairing the EFI partition does not delete user files or applications. These operations only affect the startup configuration files stored in the small system partition, leaving your main OS intact.

What should I do if the Windows Boot Manager is missing in BIOS?

You need to manually create a boot entry pointing to the bootmgfw.efi file on your Windows drive. Use the BIOS utility to browse the filesystem of the primary SSD and select the Microsoft bootloader path to re-establish the connection.

Is it safe to leave both M.2 drives connected permanently?

Absolutely. Modern systems support multiple NVMe drives simultaneously. As long as the boot order is configured correctly in the BIOS, having both drives installed poses no risk to stability or performance.

How do I know if my BIOS needs an update?

Check the current version number in the BIOS main screen against the official support page for your motherboard model. If the BIOS has trouble recognizing the second drive or lists outdated NVMe drivers, an update is recommended to improve compatibility.