i used acer aspire laptop with windows vista n it worked fine unless a little lagging but its ok.until yesterday when i open my laptop after the loading part it goes black n blank instead usually it shows welcoming part that u need to enter the password(sory i dunno the right term for that part).i tried to open it using safe mode and it goes fine but i cannot enter the password.so for conclusion is i cannot enter the windows screen.is it caused by some virus or corrupted files?n what should i do?hope u all can help me