What the Windows Boot Manager does and why you might change it

The Windows Boot Manager is the part of your system that decides which hard drive your computer starts from when you power it on. By default, it points to whichever drive Windows is installed on. You might want to change this if you've added a second drive, moved Windows to a faster drive, or need to boot from a different storage device temporarily.

Changing the boot drive is a settings change, not a data move. Your files stay where they are. You're just telling your computer to look elsewhere first when it starts up.

Key Takeaways

  • The easiest way to change your boot drive is through the BIOS or UEFI settings, which you reach by restarting your computer and pressing a specific key during startup.
  • The key you press varies by manufacturer — common ones are Delete, F2, F10, or F12 — and your computer usually displays it briefly on the startup screen.
  • Once inside BIOS or UEFI, you'll find a "Boot Order" or "Boot Priority" menu where you can move your desired drive to the top of the list.
  • If you're changing the boot drive because you moved Windows itself, you may need to repair the boot files using Windows recovery tools instead of just reordering drives.

Accessing your BIOS or UEFI settings

Your computer's BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) is the firmware that runs before Windows loads. This is where the boot order lives. To reach it, restart your computer and watch the startup screen carefully — it will display a message like "Press Delete to enter Setup" or "Press F2 for BIOS Settings."

The key varies by manufacturer. Dell, Lenovo, and HP often use F2 or Delete. ASUS and MSI frequently use Delete or F2. Acer uses F2. If you miss the window, restart again and watch more carefully — you typically have only a few seconds. If you're unsure, look up your specific computer model and "BIOS key" online.

Once you press the correct key, your computer will load the BIOS or UEFI interface instead of Windows. This looks different from your normal desktop — it's usually text-based with a dark background and menu options.

Finding and changing the boot order

Inside BIOS or UEFI, look for a menu labeled "Boot," "Boot Order," "Boot Priority," or "Boot Sequence." The exact name and location depend on your manufacturer, but it's usually in the main menu or under an "Advanced" section.

Once you find it, you'll see a list of your drives. The order matters — your computer tries to boot from the first drive in the list, then the second if that fails, and so on. Use the arrow keys to highlight the drive you want to boot from, then use the keys shown on screen (usually + and − or Page Up and Page Down) to move it to the top of the list.

After you've reordered the drives, look for a "Save and Exit" option, usually near the bottom of the menu or accessible by pressing F10. Confirm when prompted. Your computer will restart and attempt to boot from the drive you selected.

What to do if Windows won't start after changing the boot drive

If you changed the boot order but Windows doesn't start, the most common reason is that Windows isn't actually installed on the drive you selected. The boot files need to be on that drive for Windows to load. If you moved Windows to a new drive, you'll need to repair the boot files rather than just reorder the drives.

To repair boot files, restart your computer and press the key for BIOS or UEFI again. Look for an option to boot from a USB drive or recovery media. If you have a Windows installation USB, insert it and select it from the boot menu. If you don't have one, you can create one on another computer using the Windows Media Creation Tool (available free from Microsoft's website).

Once you've booted from the Windows USB, select "Repair your computer" and then "Troubleshoot." From there, you can access "Startup Repair" or "Command Prompt" to rebuild the boot files. This process varies depending on your Windows version, so search for "Windows [your version] repair boot files" if you need step-by-step instructions.

Temporarily booting from a different drive without changing settings

If you only want to boot from a different drive once — to test it, run diagnostics, or access files — you don't need to change the BIOS boot order permanently. Instead, use the boot menu.

Restart your computer and watch for a message like "Press F12 for Boot Menu" or "Press Esc for Boot Options." This key is different from the BIOS key and appears on the same startup screen. Press it, and you'll see a list of available drives. Select the one you want to boot from, and your computer will start from that drive this time only. The next time you restart, it will go back to the default boot drive.

Checking which drive is currently set as your boot drive

If you're not sure which drive your computer is currently booting from, you can check in Windows itself without entering BIOS. Open File Explorer and look at "This PC" — the drive with the Windows logo or labeled as your C: drive is usually your boot drive. You can also check in System Information: press Windows key + Pause/Break, or right-click "This PC" and select "Properties."

For a more detailed view, open Disk Management (right-click the Start button and select "Disk Management"). The drive marked as "Active" or "System" is your boot drive. If you're unsure which physical drive corresponds to which letter, look at the drive size — a 500 GB drive in Disk Management should match a 500 GB drive you see in your BIOS.

Common problems and what they mean

If you change the boot order and your computer shows an error like "No bootable device found" or "Boot failure," it means the drive you selected doesn't have Windows or bootable files on it. Go back into BIOS, move a different drive to the top, and try again. If none of your drives boot successfully, one of them may have failed or become disconnected.

If your computer boots but runs very slowly, you may have booted from an external drive by accident, or the drive you selected is failing. Check Disk Management to confirm you're on the right drive, and run a disk check if performance is poor. If you accidentally changed the boot order and want to undo it, straightforward go back into BIOS and move your original boot drive back to the top of the list.

Frequently Asked Questions

Will changing the boot drive erase my files?

No. Changing the boot order in BIOS only tells your computer which drive to start from. Your files remain on all your drives. If you're moving Windows itself to a new drive, that's a separate process that requires copying or cloning the drive, not just reordering the boot sequence.

What if I can't find the boot menu key on my startup screen?

Look up your computer model and "boot menu key" online — manufacturers list this in their documentation. Common keys are F12, F2, Esc, and Delete. If you still can't find it, try pressing each one during startup. You'll know you've hit the right key when a menu appears instead of Windows loading.

Can I set multiple drives to boot in a specific order?

Yes. In the BIOS boot order menu, you can arrange all your drives in any order you want. Your computer will try the first drive, then the second if the first fails, and so on. This is useful if you have a backup drive or want to test a new installation without removing your main drive.

Do I need to change the boot drive if I just added a second hard drive?

Only if you want to boot from the new drive. If you're just adding extra storage, you can leave the boot order as is — your computer will continue booting from your current drive, and the new drive will appear as additional storage in Windows.

What's the difference between BIOS and UEFI?

UEFI is the newer standard and is used on most computers made in the last ten years. BIOS is older. Both do the same job — they control your boot order and hardware settings. The menus look slightly different, but the process for changing the boot drive is the same in both.