My laptop, which I need for work, has been freezing randomly, always doing different things when it happens. Any audio stops, lights on keyboard won't change (when I press Caps Lock the light won't come on), the cursor won't move, the time stops, etc. Replaced the hard drive because the shop I brought it to suggested that may be the issue. I've run antivirus software and it comes back fine. Laptop used to overheat, but the shop fixed that problem and said the current issue doesn't seem to be related to that. I'm running out of ideas here. What could this be?