Computer desktop, make: Great Quality, model: GQ3081 Earlier it had windows xp service pack 2. It was being updated to service pack 3 when it started giving trouble. It was decided to install the operating system afresh. Original disk was used. The hard disk was formatted in the process of installing attempt and then it automatically tried to install the operating system.The screen then and even now reads,"Error loading operating system", whenever the computer is powered on. Hence, it has no operating system. The computer does not take any command from keyboard. Please advise Thanks.