Černá obrazovka

Zdravim. Muj kamarad ma problem. Kdyz zapne pc a prihlasi se, tak mu zcerna obrazovka. Nevite co by s tim mohlo byt?
Brian Grunkemeyer - MSFT píše:... perhaps someone w/ a broken machine can reboot into Safe Mode, run RegEdit, delete HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell then recreate the Shell key as a REG_SZ key, with the value explorer.exe.