Backup everything. First rename, then remove when you confirmed it worked. Better safe than sorry.
REM Set the new root location REM Ex. NEW_ROOT=D: REM NEW_ROOT=D:\Data REM NEW_ROOT=D:\MyStuff\MyComputer set NEW_ROOT=D: REM (Make sure that C:\Users doesn't exist anymore) move C:\Users C:\Users.Backup mklink /J C:\Users %NEW_ROOT%\Users REM DO NOT DO THE FOLLOWING REM (Rename C:\ProgramData before creating the link) move C:\ProgramData C:\ProgramData.Backup mklink /J C:\ProgramData %NEW_ROOT%\ProgramData REM Update the TEMP folder at system level setx /m TEMP %NEW_ROOT%\Windows\Temp setx /m TMP %NEW_ROOT%\Windows\Temp move C:\Windows\Temp C:\Windows\Temp.Backup mklink /J C:\Windows\Temp %NEW_ROOT%\Windows\Temp REM END DO NOT DO