Next time when you see some your files are missing and that happens often, it is the clear sign of your computer got crashed. If you could see a blue screen with some information displayed on the monitor, then is getting crashed or it has already crashed. The appearance of blue screen is due to the existence of some bad sectors in the hard drive. Next time if your system gets hanged up please do pay kind attention, because bad sector in hard drive causes system to freeze frequently. Automatic rebooting of your computer means virus in the hard drive has induced loop within the boot sectors.