What does Windows error code 134 (ERROR_IS_JOINED) mean? Status / error code: Category: Constant name: Source: Operating System: Description: An attempt was made to use a JOIN or SUBST command on a drive that has already been joined. Could be also: ConstantTypeOS ENOTCONNerrnoSolaris EPROTOerrnoWindows AUDIT_FAILUREBugCheck CodeWindows Looking for a different code? Search another status or error code.