INACCESSIBLE_BOOT_DEVICE (0x7B): Windows Lost Its Own Drive

What INACCESSIBLE_BOOT_DEVICE means in plain English

When you turn the PC on, Windows begins loading from the drive it is installed on. Partway through that start, it loses access to that same drive. It cannot safely continue without the drive, so it stops and shows INACCESSIBLE_BOOT_DEVICE with stop code 0x7B. Because the cause is still there at the next start, the same screen returns at every boot.

That screen does not mean your drive has been wiped. In most cases like this, the drive and your personal files are still there. Windows has lost the way to talk to the drive, which is different from the drive being empty or erased.

The most common trigger is a BIOS or firmware change, such as a setting that was changed or restored to its defaults. The next is a Windows update. If yours began then, the first steps for a blue screen right after an update may match your situation more closely.

A drive or cable change can also do it, for example adding a drive, moving a connection, or replacing a cable. In each case, Windows is looking for its drive in the way it was set up before, and it no longer finds that path.

Get to the recovery screen before you change anything

Do not change any settings yet. Turn the PC on, let it reach the blue screen, and let it restart on its own. After repeated failed starts, Windows should leave that loop and open the recovery screen, sometimes after showing it is preparing automatic repair. This can take several minutes, so give it time before you touch anything.

When the recovery screen appears, its heading is usually 'Choose an option;'. Select 'Troubleshoot;', then 'Advanced options;'. That second menu holds the repair tools used in the sections that follow. Do not pick a reset option here. Reaching this screen does not erase files, and you can restart and come back to it if you need a break.

From 'Advanced options;', select 'Startup Settings;' and then 'Restart;'. When the list appears, try Safe Mode once. If the desktop loads, Windows itself can still start, which makes a bad storage driver more likely than a dead drive. For the exact key choices, follow how to start in Safe Mode when your PC will not boot.

If a blue BitLocker screen asks for a recovery key instead, stop there. Do not guess the key, and do not try to work around the screen. A BIOS change can bring up this check even when the drive is fine. On a phone or another computer, find your BitLocker recovery key if that screen appears after a BIOS change, and enter it exactly as shown. Then return to the recovery screen.

The storage mode switch that often causes this on home PCs

On most home PCs, the firmware talks to the Windows drive in one of two modes: AHCI or RAID. AHCI is the standard single drive mode. RAID, often shown as Intel RST on Intel PCs, is also used on many single drive laptops, set that way by the maker at the factory.

Neither mode is better, and neither means anything is wrong with the drive itself. The trouble is a mismatch. Windows was set up with the driver for one mode, so if the firmware switches to the other, Windows starts loading, then loses its own drive and stops with INACCESSIBLE_BOOT_DEVICE (0x7B).

You do not have to have changed the setting yourself. A BIOS update, a reset to the maker's defaults, or a flat CMOS battery can put the mode back to its default value. If the blue screen began right after one of those events, this setting is the first place to check.

Open the BIOS setup screen with the key shown at startup, often F2 or Delete. Look under Storage, Advanced, or SATA settings for a line named Storage Mode, SATA Mode, or Intel RST. Write down, or take a photo of, the exact mode shown before you change anything.

Now change only that one line, to the mode the PC used before. If it now shows AHCI and the PC was on RAID, set it back to RAID, or do the reverse. Then choose 'Save and Exit;' and let the PC try to start on its own.

If Windows still will not start, go back into BIOS setup and put the setting back to the mode you wrote down. Do not guess through other settings, change several at once, or reinstall Windows. None of those fixes a flipped mode, and each one makes later checks harder.

Changing a BIOS setting can also bring up a BitLocker recovery screen on the next start. Pause and find your BitLocker recovery key if that screen appears after a BIOS change, instead of flipping the mode back just to avoid it.

If an update changed the storage driver instead

Use this route when the storage mode never changed, nothing in the BIOS was touched, and the blue screen began on the first restart after an update. The timing is the clue. An update may have replaced or damaged the driver Windows uses to read its own drive, so startup begins, then fails at the same point every time. Keep the storage mode as it is. Nothing needs reinstalling yet.

From the recovery screen, select Troubleshoot, then Advanced options, then 'System Restore;'. Choose a restore point from before the update and restart to test it. If there is no restore point, or the same screen returns, choose 'Uninstall latest quality update;' instead. See how to uninstall a bad Windows update and when you should before you use it on an older problem. Neither option deletes your personal files.

If Safe Mode loads, use it to roll back the driver instead. Open Device Manager, expand 'Storage controllers;', open the controller's properties, and on the Driver tab select 'Roll Back Driver;' if it is available. Then restart normally. If Windows reaches the desktop, the replaced driver was the cause and the older one is back in place. If that button is grayed out, use the recovery options above instead.

Check the pattern too. This failure happens early, during startup, before the sign-in screen, and repeats the same way each time. By contrast, a freeze that ends in a crash points to a different storage stop code, DPC_WATCHDOG_VIOLATION (0x133): the PC runs, then locks up for a long stretch before the blue screen appears. Treat that as a different problem. Follow that code's own fix instead.

Check that the drive itself is still seen and connected

Restart the PC and open the BIOS or UEFI setup screen, using the key shown at startup, often F2 or Delete. Look for a storage, boot, or main page that lists drives by name or size. Write down what you see before you change any setting.

If the list shows your Windows drive, the PC can still see it. That points back to the storage mode and driver checks in the earlier sections, not to a drive that has vanished. Close setup without saving changes and return to those steps.

On a desktop only, and only if you are comfortable doing it, shut the PC down, switch it off, and unplug it. Open the case and push a SATA data cable firmly into place at the drive and at the board, or check that an M.2 drive sits flat in its slot. Laptop owners should skip this step and not open the case.

If the drive never appears in the list, makes a repeated clicking sound, or appears on one start and is gone on the next, stop here. Repeated restarts will not fix that. Take the PC to a repair shop, say the drive was not listed, and ask them to protect or copy your files before any repair or replacement.

If Windows still will not start: last resorts that protect your files

Try Startup Repair once from the recovery screen. It can repair some damaged boot files, but it cannot put a storage mode back, replace a storage driver, or read a drive Windows cannot see. If the same 0x7B screen returns, running it again and again will not change the result.

Before a reinstall or a reset, get a copy of your files first. A repair shop, a technician, or a friend with a second PC can often copy the drive's contents to another drive. Tell them not to format, reset, or reinstall anything until that copy is done or has been tried.

Only after that backup should you consider resetting or reinstalling Windows. Read what Keep my files and Remove everything really mean before you reset so you know what each choice keeps and removes. Do not treat either choice as a safe place to start if your files are not copied yet.

Skip any driver updater or cleaner download offered as a fix for this code. A program like that cannot run on a PC that will not start, and some such offers lead to charges or unwanted software. Stick to the recovery tools already on the PC and to help in person if you need it.

Frequently asked questions

Does INACCESSIBLE_BOOT_DEVICE mean my files are gone?

Usually no. 0x7B means Windows could not reach its drive during startup. The files are often still on the drive, which is why copying them comes before any reset or reinstall.

Can I try both AHCI and RAID to see which one works?

Do not guess back and forth. Write down the current mode first, test the original mode once, and put the setting back if Windows still shows 0x7B. Repeated blind changes make the cause harder to track.

Conclusion

For most home PCs, INACCESSIBLE_BOOT_DEVICE (0x7B) ends when Windows can use the storage setting or driver it was set up with again. Work in the order above, change one thing at a time, and write down each original setting before you touch it.

If none of those checks brings Windows back, stop before a reset or reinstall and protect your files first. A repair shop that copies the drive before replacing parts or rebuilding Windows is the safer next call, even if the drive itself turns out to have failed.