What does Windows error code 149 (ERROR_IS_SUBST_TARGET) mean? Status / error code: Category: Constant name: Source: Operating System: Description: An attempt was made to join or substitute a drive for which a directory on the drive is the target of a previous substitute. Could be also: ConstantTypeOS EALREADYerrnoSolaris PNP_INTERNAL_ERRORBugCheck CodeWindows Looking for a different code? Search another status or error code.