STOP is usually the code given on the front of the box as it is about to restart, or, is being restarted by holding down the power button on the front of the box. This behaviour could have been triggered by overheating, but as you've advised something got noisy, possibly some internal circuitry has failed causing the box to stay offline.
If you believe the device is problematic and is generating excess amounts of heat your first port of call should always be to get a Virgin Engineer out to repair or replace, after all, that is one of Virgin Media's selling points. Based on what you have advised, the heat and noises, I would call technical support immediately.
Additionally, you can ensure that the box is in a well ventilated space, and depending on where its air vents are, you should ensure that there is sufficient airflow around it. Avoid putting your box on a wooden or carpeted surface and keep it flat instead of on it's side as this will allow heat to dissipate quicker instead of radiating onto other components.
Welcome to the forum. I'm really sorry to hear of the problems you're having with the box overheating. This doesn't sound good so I'd like to arrange an engineer visit to check things over. I'll send you a PM (purple envelope, top right corner) to get this arranged.