The sound on my laptop has RECENTLY been going on and off; it goes from muted to unmuted. Also the sound display box pops up to show that it is muted/unmuted - the sound box that pops up when you turn the volume up/down from the laptop's keyboard (by holding Fn+up)...but he keyboard on my laptop has not been working for a few months (spilled something on it).

So I'm thinking that the keyboard might be fried or a key is stuck?

Also I noticed while typing this that it occasionally backspaces while i'm typing?I would go with the keyboard causing the problems, then...liquid damage can cause all sorts of problems, and it sounds as if some of the keys are RANDOMLY ACTIVATING.  If you're not using the keyboard at all, and using an external keyboard, you COULD remove the laptop's keyboard, or better just unplug it as the keyboard will usually prevent dust etc getting inside the laptop.  Alternatively, replace it or have it REPLACED, but with liquid damage I would want to ensure there's no liquid elsewhere in the laptop to cause problems later on.