
EDIT: I have just listened closely and the noise is actually coming from the lengthways vent above the red circle (where the HDMI cable plugs in). I believe this is the graphics card.
This morning our HP Omen desktop started making a very loud vibration noise (to the point i thought it was the washing machine!). I have restarted and left off etc and it makes no difference. Loud noise from start up and doesnt seem to depend on load.
The image with the red highlights is where the noise is coming from. When you press down on the metal where I have highlighted it red, the rattling reduces (which i assume is the metal cover on the back vibrating) but htere is still a loud vibration and rattling noise coming from the PC that doesnt get louder or quieter, just stays very loud.