STATUS_NO_LOG_SPACE (0XC000017D) — registry log full fix

Quick answer

Reboot into safe mode, delete the registry log files at C:\Windows\System32\config\RegBack and C:\Windows\System32\config\*.LOG*, then reboot normally. If that fails, use the registry backup from RegBack but only as a last resort.

Why this happens

This error means the registry transaction log — Windows' way of tracking pending hive writes — has hit its size limit. The culprit here is almost always a buggy driver or a failed Windows update that keeps hammering the registry with writes. I've seen it on Server 2012, 2016, and even Windows 10 1809 onward. The registry log files (like SYSTEM.LOG1, SOFTWARE.LOG2) are supposed to roll over automatically, but when the hive is corrupt or the disk is nearly full, they don't. The system throws 0XC000017D and often won't boot past the spinning dots.

Don't bother with chkdsk first — it rarely helps here unless your disk is actually at 99% capacity. Check free space, but 9 times out of 10 it's the logs.

Fix steps

1. Boot into safe mode with command prompt. Mash F8 during boot or interrupt the startup 3 times to get recovery options. If you can't get into safe mode, use a Windows installation USB and select Repair your computer > Troubleshoot > Command Prompt.
2. Check disk space. Run dir C:\ in the command prompt. If C: is under 500MB free, free up space by deleting temp files or moving data. This alone can fix the error.
3. Delete the log files. Run these commands one by one:

   del /f /s /q C:\Windows\System32\config\*.LOG1
   del /f /s /q C:\Windows\System32\config\*.LOG2
   del /f /s /q C:\Windows\System32\config\*.blf

   Also delete C:\Windows\System32\config\RegBack\*.LOG* and C:\Windows\System32\config\RegBack\*.blf if they exist. Don't delete the actual hive files (like SYSTEM, SOFTWARE, SAM).
4. Reboot normally. Exit safe mode and restart. The system will recreate the log files on next boot. If it still fails, go to the alternative fixes below.

Alternative fixes

Restore from registry backup — but only if the above fails. Windows keeps a backup in C:\Windows\System32\config\RegBack. Copy the files from that folder to C:\Windows\System32\config, overwriting the existing ones. This will roll back your registry to an older state, so some installed programs or settings may vanish. Use this command:

copy /y C:\Windows\System32\config\RegBack\* C:\Windows\System32\config\

Last resort: system restore or repair install. Boot from a Windows USB, select Repair your computer > Troubleshoot > System Restore. Pick a restore point from before the error started. If you don't have one, do an in-place upgrade (repair install) using the same USB — it keeps your files and apps but replaces system files.

Prevention tip

Once you're back in Windows, check your disk for bad sectors. Use this in an admin command prompt:

chkdsk C: /f /r

If this error keeps coming back, you've got a driver or service that's leaking registry writes. Run procmon from Sysinternals and filter on registry writes — find the process that's flooding the hive and update or remove it.