Engine noise

I have a 2000 4x4 Expedition. 130,000 miles. I've been noticing an engine noise. It sounds like power steering whine but it's coming from the passenger side of the engine. Almost like it's coming from the valve cover or timing chain. I haven't ruled out the altenator either. When I shut the truck off, it whines for about 2 more seconds. Kind of like the serpentine belt is still turning whatever is making the noise. Will the electronics be harmed if I unplug the alt. and start it for a couple of minutes?