What does Windows error code 137 (ERROR_NOT_SUBSTED) mean?

ERROR_NOT_SUBSTED

What ERROR_NOT_SUBSTED means

ERROR_NOT_SUBSTED is a Win32 system result whose documented message is: “The system tried to delete the substitution of a drive that is not substituted.” In practical troubleshooting, it belongs to attempts to delete a SUBST mapping from a drive letter that is not presently substituted.

Typical causes

• the mapping was removed manually before automated cleanup
• the command runs in a different session from the one that created the mapping
• the application recorded stale mapping state

How to investigate the result

1. query SUBST state from the same token and session as the failing process
2. Compare the intended letter with normalized current mappings
3. Review whether cleanup is repeated during shutdown

Developer guidance

Design deletion as an idempotent transition to “mapping absent.” Distinguish benign absence from a letter now backed by a real volume.

Administrator and support guidance

Do not force removal until confirming what currently owns the letter. A physical or network drive with the same letter is not the old SUBST mapping.

Example

A service tries to remove a user-session SUBST mapping but cannot see that session’s mapping and receives this result.

How it differs from related results

It reports that no substitution exists; it is not evidence that the destination directory is missing.

References

• Microsoft: System error codes 0–499