Diskpart: Make Partition Inactive (Deactivate an Active Partition)

Making an Active Partition Inactive Using Diskpart

If a partition has been accidentally set active — and you haven’t restarted the machine yet — you can undo it with Diskpart before it causes a boot issue. Open an elevated Command Prompt and run:

diskpart
list disk
select disk 0
list partition
select partition 1
inactive

Adjust the disk and partition numbers to match your actual system — use list disk and list partition to see all disks/partitions and their numbers before selecting, rather than assuming disk 0/partition 1 is correct for your machine. Once you’ve selected the right partition, inactive clears the active flag on it. If the machine has already been restarted with the wrong partition marked active and it’s now failing to boot correctly, you may need to boot from Windows installation media into the Recovery Environment to run these same Diskpart commands from there instead.

Running This from Windows Recovery Environment

If you’re already at the point of booting from install media because the machine won’t start, the process is the same but reached slightly differently: on the “Choose an option” screen, go to Troubleshoot > Advanced options > Command Prompt instead of clicking Install. That opens a command prompt inside the recovery environment, where you run the exact same diskpart sequence above. One difference to watch for: disk and partition numbers can occasionally be reported differently in the recovery environment than they were in normal Windows, so re-run list disk and list partition from scratch here rather than reusing numbers you noted down earlier.

Why a Partition Being “Active” Matters

The active flag tells the BIOS/legacy boot process which partition contains the boot loader it should hand control to at startup — only one partition per disk should normally be marked active, and it needs to be the one actually containing (or pointing to) a working boot loader. Marking the wrong partition active is what causes the boot failure in the first place; this fix works by simply removing that incorrect flag so the system stops trying to boot from the wrong place. Note this concept applies to legacy BIOS/MBR-style booting — UEFI systems using GPT disks handle the boot partition designation differently (via the EFI System Partition) and don’t use the same active-flag mechanism, so if you’re on a UEFI/GPT system, an “active partition” issue in this specific sense doesn’t apply.