BI/OS beeping and pock-ing

[signorigianmario]

Hi there. I have a Acer Aspire 5740G, i5 version, received from my sister 2 years ago. I've noticed that the laptop has 8GB RAM instead of 4GB RAM (at least that's what the glued label says). I don't think that could be the problem.
But the problem itself is that: only after a ~2 hours of continuously use, a long beep (1 second) and a pock comes out. I think that the beep comes from the BI/OS (I know that this is the only component that makes beeps). I tought that the temperature can be the problem, but I have a cooler under the laptop. Can this thing harm my laptop?

P.S.:Laptop's specs: Intel Core i5-430M (2.26 GHz - 2.27 GHz up to 2.53 GHz), 932 GB HDD (but the laptop came from factory with 500 GB HDD), 8 GB RAM (4GB from the factory), AMD Mobility Radeon 5650, BI/OS: Phoenix Technologies, came with Windows 7 HP x64 but 8.1 x64 (current OS) seems to behave much better than Windows 10 or 7.

 

[hang-the-9]

What is a "pock"? Does it beep once only? Try to get a video of this happening and post a link to it.

 

[signorigianmario]

What is a "pock"? Does it beep once only? Try to get a video of this happening and post a link to it.

it's a pock like you just touch a plastic with your nail. And I can't know exactely when this happens because it's apporximately 2 hours, +/-.

 

[hang-the-9]

What is a "pock"? Does it beep once only? Try to get a video of this happening and post a link to it.

it's a pock like you just touch a plastic with your nail. And I can't know exactely when this happens because it's apporximately 2 hours, +/-.

Oh, a "pop"? No way to say what it may be or what may cause it without seen/hearing it, have a local tech look it over.