It was my fault really. I didn't update the anti-virus software (I'm a cheapskate), and then I got a virus from Facebook. When I ran the repair disc, it wiped the entire thing. Then I was told to run start-up disc from the company I bought it from, everything stopped working gradually. First it was the Preferences, then audio, video and network cards, then the physical equipment (keyboard, mouse speakers). But everything is all right now, though.