Ok so I got my dad's old laptop. I've had it for almost three-four months now and I love it. but recently, well before I got it, on random occasions it will just lock up on me. The motor(or whatever that humming in the laptop is) is still running but my laptop literally locks up. I can't do anything but shut it off by the power button.....Everything the computer is doing is locked and froze. I've dealt with it long enough but I"m use to leaving my computer on, but now I have to put it in stand by when I"m bout to leave the computer for a long period of time. The times the computer locks up are strictly random. Some days I"m lucky enough not to have my computer lock up. Other days I may experience this five times a day.....What could be causing this. The laptop is a Sony Vaio and its about three-four years old.