Fix Hard Drive Error 0x000000ED in 3 Steps

The 30-Second Fix: Boot Configuration Repair

Error 0x000000ED (UNMOUNTABLE_BOOT_VOLUME) hits when Windows can't talk to your boot drive during startup. The simplest fix? Rebuild the boot configuration data (BCD). This works about 40% of the time.

1. Boot from your Windows installation media. A USB stick or DVD works.
2. On the first screen, click Repair your computer (bottom-left corner).
3. Go to Troubleshoot > Advanced options > Command Prompt.

Once the command prompt opens, run these three commands in order:

bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd

Reboot. If the error's gone, you're done. If not, move on.

The 5-Minute Fix: Check Disk for Corruption

If the boot config wasn't the problem, the issue is likely file system corruption on the boot drive. This is common after a sudden power loss or a bad shutdown.

From the same Command Prompt (boot from media again if you already rebooted), run:

chkdsk C: /r

Wait—it'll take a few minutes. The /r flag locates bad sectors and recovers readable info. If your system drive isn't C:, replace the letter. You can find the right drive by typing diskpart, then list volume.

After chkdsk finishes, type exit and reboot. If the error persists, you've got a deeper issue—likely a bad driver or failing hardware.

The 15+ Minute Fix: Storage Driver Reset

Here's the culprit most people miss: Windows loads the wrong storage controller driver during boot. This happens if you've recently switched between AHCI and IDE modes in BIOS, or after a motherboard swap without reinstalling.

Step 1: Boot into Safe Mode

If you can get to the Advanced Boot Options (press F8 during startup, or use the recovery environment), select Safe Mode. If you can't, boot from your installation media again, go to Repair your computer > Troubleshoot > Advanced options > Startup Settings > Restart. After restart, press 4 for Safe Mode.

Step 2: Reinstall the Standard Driver

Once in Safe Mode:

1. Right-click Start and open Device Manager.
2. Expand IDE ATA/ATAPI controllers.
3. Right-click your storage controller (usually Standard SATA AHCI Controller or Intel(R) 6 Series/C200 Series Chipset) and select Update driver.
4. Choose Browse my computer for drivers > Let me pick from a list.
5. Select Standard SATA AHCI Controller (or Standard Dual Channel PCI IDE Controller if you're on IDE mode).
6. Click Next and reboot.

If Safe Mode won't load (it happens), you can force the driver swap from the recovery environment's Command Prompt:

dism /image:C:\ /remove-driver /driver:"C:\Windows\System32\drivers\iastor.sys"
dism /image:C:\ /add-driver /driver:"C:\Windows\Inf\msahci.inf"

That removes the Intel-specific driver and forces the generic Microsoft AHCI driver. Adjust the paths if your Windows drive isn't C:.

Step 3: Verify BIOS Settings

While you're at it, reboot into BIOS/UEFI and check the SATA mode setting. It should match the driver you installed. If it's set to RAID but you're using AHCI, switch to AHCI. If you're on an older machine with IDE mode, set it to IDE. Mismatch between BIOS and driver is the #1 cause of this error.

When to Give Up and Replace the Drive

If none of these steps worked, your hard drive is likely dying. Run a SMART diagnostic from the recovery environment—if you see Reallocated Sectors or Current Pending Sectors in the triple digits, the drive is toast. Back up what you can (using a live Linux USB if necessary) and replace it.

This error is almost never a software problem once you've ruled out corruption and drivers. I've seen it happen on Dell OptiPlex 3020s and HP EliteDesk 800 G2s with failing Seagate drives. Don't waste hours on bandaids—swap the drive.