Each time we reinstalled Windows, it will create a new SID for user even the username is as same as before. // example (not real SID format, just show the problem) user SID -------------------- liuyan S-old-501 // old SID before reinstall liuyan S-new-501 // new SID after reinstall The annoying problem after reinstall is NTFS file owership and permissions on hard drive disk are still associated with old user's SID. I want to keep the ownership and permission setting of NTFS files, then want to let the new user take the old user's SID, so that I can access files as before without permission problem. The cacls command line tool can't be used in such situation, because the file does belongs to new user, so it will failed with Access is denied error. and it can't change ownership. Even if I can change the owership via SubInACL tool, cacls can't remove the old user's permission because the old user does not exist on new installation, and can't copy the old user's permission to new user. So, can we simply bind old user's SID to new user on the freshly installed Windows ? Sample test batch @echo off REM Additional tools used in this script REM PsGetSid http://technet.microsoft.com/en-us/sysinternals/bb897417 REM SubInACL http://www.microsoft.com/en-us/download/details.aspx?id=23510 REM REM make sure these tools are added into PATH set account=MyUserAccount set password=long-password set dir=test set file=test.txt echo Creating user [%account%] with password [%password%]... pause net user %account% %password% /add psgetsid %account% echo Done ! echo Making directory [%dir%] ... pause mkdir %dir% dir %dir%* /q echo Done ! echo Changing permissions of directory [%dir%]: only [%account%] and [%UserDomain%\%UserName%] has full access permission... pause cacls %dir% /G %account%:F cacls %dir% /E /G %UserDomain%\%UserName%:F dir %dir%* /q cacls %dir% echo Done ! echo Changing ownership of directory [%dir%] to [%account%]... pause subinacl /file %dir% /setowner=%account% dir %dir%* /q echo Done ! echo RunAs [%account%] user to write a file [%file%] in directory [%dir%]... pause runas /noprofile /env /user:%account% "cmd /k echo some text %DATE% %TIME% > %dir%\%file%" dir %dir% /q echo Done ! echo Deleting and Recreating user [%account%] (reinstall simulation) ... pause net user %account% /delete net user %account% %password% /add psgetsid %account% echo Done ! %account% is recreated, it has a new SID now echo Now, use this "same" account [%account%] to access [%dir%], it will failed with "Access is denied" pause runas /noprofile /env /user:%account% "cmd /k cacls %dir%" REM runas /noprofile /env /user:%account% "cmd /k type %dir%\%file%" echo Done ! echo Changing ownership of directory [%dir%] to NEW [%account%]... pause subinacl /file %dir% /setowner=%account% dir %dir%* /q cacls %dir% echo Done ! As you can see, "Account Domain not found" is actually the OLD [%account%] user echo Deleting user [%account%] ... pause net user %account% /delete echo Done ! echo Deleting directory [%dir%]... pause rmdir %dir% /s /q echo Done !