FAQ
TL;DR: On some Windows 10 PCs, over 900 GB on a 1 TB drive appears unusable; "You cannot perform operations on a system partition from the system booting from it." Use bootable tools or reinstall to reclaim space. [Elektroda, DriverMSG, post #16793473]
Why it matters: This FAQ helps Windows 10 users fix greyed‑out Extend Volume and recover missing disk space on new or cloned drives.
Quick-Facts
- Symptom: 1 TB disk shows only ~118–120 GB allocated; Extend Volume is disabled in Disk Management. [Elektroda, poole18, post #16793168]
- Finding: A single hidden partition of 900+ GB can exist even when C: reports ~118 GB. [Elektroda, DriverMSG, post #16793178]
- Constraint: You can’t resize the active system partition while booted from it; use a LiveCD/USB. [Elektroda, DriverMSG, post #16793473]
- Resolution path: The OP reclaimed capacity by reinstalling Windows, which rebuilt partitions. [Elektroda, poole18, post #16796461]
- Health check: SMART looked healthy; layout, not hardware, caused the issue. [Elektroda, DriverMSG, post #16793689]
Quick Facts
- Symptom: 1 TB disk shows only ~118–120 GB allocated; Extend Volume is disabled in Disk Management. [Elektroda, poole18, post #16793168]
- Finding: A single hidden partition of 900+ GB can exist even when C: reports ~118 GB. [Elektroda, DriverMSG, post #16793178]
- Constraint: You can’t resize the active system partition while booted from it; use a LiveCD/USB. [Elektroda, DriverMSG, post #16793473]
- Resolution path: The OP reclaimed capacity by reinstalling Windows, which rebuilt partitions. [Elektroda, poole18, post #16796461]
- Health check: SMART looked healthy; layout, not hardware, caused the issue. [Elektroda, DriverMSG, post #16793689]
Why is Extend Volume greyed out on my Windows 10 C: drive?
Windows blocks resizing the active system partition while it’s running. Boot from external media to manage it. “You cannot perform operations on a system partition from the system booting from it.” [Elektroda, DriverMSG, post #16793473]
Where did the missing space on my 1 TB drive go?
A large partition (over 900 GB) can exist but remain unusable from your current layout view. Tools can reveal it even if C: shows ~118 GB. [Elektroda, DriverMSG, post #16793178]
Is my hard drive failing or is it a partition problem?
SMART reported the disk as healthy. The problem stemmed from how partitions were created or cloned, not from hardware failure. [Elektroda, DriverMSG, post #16793689]
What caused only ~118 GB to be usable on a 1 TB disk?
The system appears cloned from a smaller drive, leaving a 127 GB system partition and messy GPT entries. That layout blocks expansion. [Elektroda, conan02, post #16793350]
What is bootable software and why do I need it?
It’s software that runs from a USB/CD instead of your system drive. “Software that runs from a pen drive, CDRom, other data carrier than your system/disk.” Use it to safely edit partitions. [Elektroda, DriverMSG, post #16793719]
How do I extend C: to use the unallocated space (three steps)?
- Create a bootable USB with a tool like GParted or EaseUS.
- Boot from the USB, then view the disk’s partition layout.
- Delete/merge stray entries if needed and extend C: into free space, then apply changes.
“Linux LiveCD, Gparted, Easeus etc.” [Elektroda, DriverMSG, post #16793719]
Can I fix this without reinstalling Windows?
Yes, with bootable partition tools and care. However, the OP chose a full reinstall, which rebuilt partitions and restored capacity cleanly. [Elektroda, poole18, post #16796461]
What is DMDE, and why did someone ask for its layout view?
DMDE is a disk editor/recovery tool used to inspect detailed partition layouts. A layout screenshot helps experts pinpoint malformed entries. [Elektroda, DriverMSG, post #16793178]
What do “Noname 02 BCF” and “EBCF” entries mean?
They refer to partition records: BCF indicates a valid entry; EBCF indicates a damaged, incorrectly recorded one. Fixing the table restores access. [Elektroda, mati211p, post #16794044]
I can’t connect the drive to another PC—what now?
Boot from a LiveCD/USB on the same PC. You can then work on C: safely because it isn’t the running system. That enables extend/repair. [Elektroda, DriverMSG, post #16793473]
When should I use warranty service instead of DIY tools?
If the disk shows errors or you’re unsure, choose warranty. The expert outlined two tracks: warranty or bootable software. [Elektroda, DriverMSG, post #16793689]
Will trying to extend partitions risk data loss?
Yes. Missteps or rebuilds can remove recovery partitions and force reinstalls. One case reconfigured to a 127 GB system partition. Back up first. [Elektroda, conan02, post #16793350]
Why does Disk Management show 118.19 GB at the top but 1 TB at the bottom?
The volume list reports the active 118.19 GB partition, while the disk map shows total capacity. The snap-in display can mislead. [Elektroda, conan02, post #16793197]
Is a clean reinstall a valid fix for this layout?
Yes. A reinstall can wipe incorrect entries and rebuild GPT, reclaiming the full 1 TB. That’s how the OP resolved it. [Elektroda, poole18, post #16796461]
What’s the edge case I should watch for after recovery?
Recovery tools may recreate only a ~127 GB system partition, leaving the rest unused. Verify sizes before finishing. [Elektroda, conan02, post #16793350]
