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ERROR_SAME_DRIVE
What ERROR_SAME_DRIVE means
ERROR_SAME_DRIVE is a Win32 system result whose documented message is: “The system cannot join or substitute a drive to or for a directory on the same drive.” In practical troubleshooting, it belongs to legacy JOIN or SUBST validation that rejects mapping a drive to a directory located on that same drive.
Typical causes
- the target path resolves back to the source drive
- an environment variable changed and created a self-reference
- path normalization exposed a same-volume mapping that string comparison missed
How to investigate the result
- resolve source and target to volume identifiers, not only drive letters
- expand environment variables and symbolic components
- Check for self-referential or circular configuration
Developer guidance
Validate mappings after canonical resolution and prohibit self-reference before issuing the operating-system command.
Administrator and support guidance
Correct the target to a directory on a different drive or remove the unnecessary mapping. Do not try to bypass this guard.
Example
A configuration expands the target for drive D: to D:\LegacyRoot, so the attempted mapping fails with this result.
How it differs from related results
It prevents a direct self-mapping, while JOIN_TO_JOIN and related codes reject more complex chained topologies.
References
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