My computer refuses to start please help!?

Around a month ago I had been working on my desktop computer in the morning, went to school and returned home to find my computer in some kind of hibernation/sleep mode. I could not do anything to get the computer to resume so my only option was to hold down the power button and restart it. This continued to happen to me everyday. It got increasingly frequent and so I began worried and attempted to virus scan. I managed to scan some of my drives, however when attempting to run a full scan my computer would go into this "hibernate mode" during the scan and I would have to restart the computer therefore not achieving anything from the scan. The computer exponentially oftenput itself into this mode so I copied everything I could want onto my external hard drive. It has now gotten to the stage where I start up the computer, get asked if I want to run windows in normal mode or safe mode etc. Even when choosing safe mode the computer "hibernates" almost immediatly. Btw this "hibernate mode" consists of my screen turning itself off, but the hard drive is still on. I would rather not have to upgrade my computer and would therefore like to get it working again. The thing is I'm not sure whether it is a firmware issue, hardware, or some kind of virus. So if possible I would like to be able to remove said "virus" and continue using the computer. If that is not possible, Re-boot the computer with the original factory software and settings, although I do not have original disks. The computer did have a recovery drive. Can supply the make model etc. if nessessay. Please help!!!