This policy setting specifies whether Remote Desktop Services retains a user's per-session temporary folders at logoff.You can use this setting to maintain a user's session-specific temporary folders on a remote computer even if the user logs off from a session. By default Remote Desktop Services deletes a user's temporary folders when the user logs off.If you enable this policy setting a user's per-session temporary folders are retained when the user logs off from a session.If you disable this policy setting temporary folders are deleted when a user logs off even if the server administrator specifies otherwise.If you do not configure this policy setting Remote Desktop Services deletes the temporary folders from the remote computer at logoff unless specified otherwise by the server administrator.Note: This setting only takes effect if per-session temporary folders are in use on the server. If you enable the Do not use temporary folders per session policy setting this policy setting has no effect.
Windows Components\Remote Desktop Services\Remote Desktop Session Host\Temporary folders
Machine
At least Windows Server 2003
HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services!DeleteTempDirsOnExit
TerminalServer.admx