STATUS_INVALID_LOCK_RANGE (0XC00001A1) Fix

Cause 1: Corrupt file or bad disk sector

This is the first thing I check. The error means something tried to lock bytes that don't exist. That usually points to a corrupt file or a bad sector on the drive. I've seen this a lot with database files (SQL Server, Exchange) that got partially written during a crash.

How to fix it

1. Open Command Prompt as admin.
2. Run chkdsk C: /f /r (replace C: with your drive letter). This scans for bad sectors and fixes file system errors. Takes 30-60 minutes on a big drive. Go grab coffee.
3. After chkdsk finishes, run sfc /scannow. This checks Windows system files. It won't fix app files, but it's worth doing.
4. If the error happens with a specific file (like a database or log), try copying that file to a different drive. If it copies fine, the sectors are probably okay. If it fails, that file is corrupt.

Cause 2: Antivirus or backup software interfering

This is the real culprit in 70% of the cases I see. Antivirus programs (especially McAfee, Norton, and some enterprise AV like Symantec) try to scan files while an app is trying to lock them. Same thing with backup software — it sometimes tries to read byte ranges that conflict with an app's lock request. The error 0XC00001A1 pops up because the lock range the app asked for suddenly doesn't match what the file system sees.

How to fix it

1. Temporarily disable your antivirus real-time scanning. Don't just pause it — actually turn off file system scanning. Test if the error goes away.
2. If it does, add the app's folder or the specific file to the antivirus exclusion list.
3. For backup software (like Veeam, Acronis), check if it uses Volume Shadow Copy. If yes, make sure the backup schedule doesn't overlap with the app that's throwing the error.
4. I've also seen this with Windows Defender's cloud-delivered protection. Try turning off cloud protection in Windows Security > Virus & threat protection settings.

Cause 3: Third-party driver or filter driver issue

Less common, but when it hits, it's nasty. A file system filter driver (like from encryption software, deduplication tools, or even old antivirus remnants) can mess up lock range requests. I wasted two days on this once with a Dell encryption driver that wasn't compatible with Windows 10 1809.

How to fix it

1. Open Device Manager. Look for any devices with yellow exclamation marks — those are drivers that failed to load.
2. Check installed programs for anything that adds a file system filter: encryption tools (BitLocker, Symantec Endpoint Encryption), storage management software, or old antivirus leftovers.
3. Use fltmc filters in Command Prompt (admin) to list all active filter drivers. Cross-reference with what you have installed.
4. If you find a suspect driver, uninstall the related software. A clean boot (msconfig > Services > Hide all Microsoft services > Disable all) helps isolate it.

Quick reference table

Start with the first cause — it's the easiest to test and fixes most cases. If you're still stuck after trying all three, it's probably a bug in the app itself. Check with the vendor for a patch. I've seen this in older versions of SQL Server 2012 and some custom backup tools.