Restabelecer o mapeamento B:
:
powercfg -change -standby-timeout-ac 0
if not exist B:\desktop\nul net use B: \ComputerName\ShareName /PERSISTENT:No
robocopy "C:\USER\DESKTOP\" "B:\DESKTOP"
powercfg -change -standby-timeout-ac 1
shutdown /s -t 0
ou, com teste diferente:
powercfg -change -standby-timeout-ac 0
net use b:
if %errorleve% NEQ 0 net use B: \ComputerName\ShareName /PERSISTENT:No
robocopy "C:\USER\DESKTOP\" "B:\DESKTOP"
powercfg -change -standby-timeout-ac 1
shutdown /s -t 0