Windows System Log · Event 55
Event 55: NTFS found corruption on a volume
The file system on a drive is damaged. Windows usually schedules a repair automatically, but the corruption itself has a cause — most often failing storage or an unclean shutdown — and repairing without finding that cause means it will come back.
Also written as Event ID 55Ntfs 55
- How oftenUncommon
- Vendor calls itError
- LogSystem
- SourceNtfs
What it means for you
On a personal computer
The organisation of files on your drive is damaged. Windows will usually fix it at the next restart. Back up first, and if it happens more than once the drive itself is probably at fault.
For an analyst
Treat repeated corruption on the same volume as a storage or power problem, not a file system one. On virtual machines, check host storage and whether the guest is being reset unexpectedly.
What it looks like
Sanitised. Addresses come from the RFC 5737 documentation ranges.
A corruption was discovered in the file system structure on volume C:.
The exact nature of the corruption is unknown. The file system structures need to be scanned online.The fields that decide it
Everything else in the log line is context.
- Volume
- Which volume is affected, identified by drive letter or volume GUID.
- Reference number
- An internal file reference for the damaged structure. Useful mainly to Microsoft support.
- Corruption description
- What was found. Some variants are minor and repaired transparently; others require a full chkdsk.
Ordinary reasons this happens
Most of the time it is one of these.
- An unclean shutdown or power loss while files were being written.
- A removable drive disconnected while in use.
- A one-off software fault during a write, which the automatic repair resolves permanently.
What to do next
- Back up the volume before running any repair.
- Check whether Windows has already scheduled a repair, and let it run.
- Look for disk errors — Events 7, 51, and 129 — around the same time.
- Check whether the machine has been shutting down uncleanly, using Events 6008 and 41.
- If corruption recurs on the same volume, replace the drive or fix the underlying storage rather than repairing repeatedly.
- On virtual machines, check host storage health and whether the guest is being reset.
Queries to run
Get-WinEvent -FilterHashtable @{LogName='System'; ProviderName='Ntfs'} -MaxEvents 50 | Select-Object TimeCreated, Id, Message | Format-ListRepair-Volume -DriveLetter C -ScanCommon questions
How do I fix NTFS corruption reported by Event 55?
Back up first, then let Windows run its scheduled repair, or run `Repair-Volume -DriveLetter C -Scan` to check and `-SpotFix` to repair. If corruption returns on the same volume, stop repairing and find the cause — that is nearly always failing storage or repeated unclean shutdowns.
Does Event 55 mean I will lose files?
Not necessarily. Most corruption Windows reports is in file system metadata rather than file contents, and the automatic repair resolves it without data loss. That said, corruption is a signal that something is wrong with the storage or the shutdown behaviour, so back up before repairing rather than after.
Read next
- Usually comes before Event 7: The device has a bad block Bad blocks, a common cause of file system corruption.
- Usually comes before Event 51: A paging error on a disk Paging errors on the same drive.
- Usually comes before Event 6008: The previous system shutdown was unexpected An unexpected shutdown, the other common cause.
- Read alongside Event 129: A storage controller reset the drive Controller resets, which interrupt writes mid-flight.
Vendor documentation
Last reviewed 28 August 2026