Update your post to include full system hardware specs and OS information.
Include PSU: make, model, wattage, age, condition?
Disk drives: make, model, capacity, how full?
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I think the noise is a fan - the source location needs to be clearly identified.
Appears to have some resonance - note the "throbbing"/"pulsating" effect.
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There are other problems:
Video shows much dust and dirt. Fans could be out of balance, air flows being blocked causing fans to overwork due to higher temperatures.
Power down, unplug, "open up" for full cleaning.
Clean out dust and debris. Use canned air to do so. Follow the instructions.
Verify that all cards, connectors, RAM, and jumpers are fully and firmly connected.
Inspect for signs of damage: bare conductor showing, wires kinked or pinched, loose components, signs of melting, browned or blackened components, swollen components.
Determine if the noise ends.
If not, then pinpoint the location of noise:
Use a cardboard tube or rolled up sheet of paper to carefully move about and focus your hearing on all fans and HDD's (if any).
And be careful with that screwdriver. Touching the wrong pins could end badly....