Constant screeching/beeping sound coming from inside of Computer?

[StudmuffinzYT]

Didn't first start out with this noise, it was a quite pc, (HP pavilion 500-214) but after a couple months, A electrical beeping/screetching sound can be heard from within the PC, hard to pin point from what without taking off case and looking, but Basically its a constant faint annoying screetch from within, when I type, or move my mouse, it toggles it, plays with the sound, if i wiggle my mouse or type, the sound goes quiet and back to normal with every click or movement.
Sometimes if I run a program, the sound stops all together... Very weird...
what could it be?

 

[V1ctor89]

It could either be a fan that is not well greased or it could be the hdd (has mechanical parts inside). You could start by applying some fine oil to the fan's rotor (can be accessed from the back, there is a label or a rubber cap hiding it). Then you can remove the hdd from the case, but keep it connected to the cables and get your ear close to it and listen. This should make it clear if the sound comes from inside. Also, make sure you apply oil to EVERY fan (CPU, case, GPU, PSU).

 

[StudmuffinzYT]

It could either be a fan that is not well greased or it could be the hdd (has mechanical parts inside). You could start by applying some fine oil to the fan's rotor (can be accessed from the back, there is a label or a rubber cap hiding it). Then you can remove the hdd from the case, but keep it connected to the cables and get your ear close to it and listen. This should make it clear if the sound comes from inside. Also, make sure you apply oil to EVERY fan (CPU, case, GPU, PSU).

I don't see how a fan could be the issue, The fan shouldnt be able to change its sound by me moving my mouse or typing. ?