hey amanush wat i thnk is that u or somebody who used ur comp has changed the power saving settin knowingly or unknowingly. so go to the "contol panel" then go to "power option" menu n change the settin like turn off ur monitor or turn off ur harddisk to never or how frefuently u want ur comp tob off. if that works gud for u if not try downloadin new antivirus from net. could b new spyware which ur antivirus isn't able to detect. let me know if it worked =)