It may have been a quite stupid and imprudent idea, but I put blankets over my tv as well as on top of my Xbox (specfically cotton blankets) for about 9 hours.
I wake to hear my Xbox fan is loud, don't have to guess twice that its overheating because of all the air being blocked out. The Xbox 360 horizontally ontop of my tv black box, and is about 5 inches in front of a wall, so it's not entirely in a closed space.
What I'd like to know is will it soon blow up and develop the red ring of death? It's never done this before, sure it gets hot but it never has gotten to the point where the fan is loud. I had 2 fans blowing on the Xbox to cool it down for about 10 minutes, both were blowing on every side of the Xbox; also opened the disctray, and blew that with cold air as well. Does any of that help the cause in hopes the Xbox returns to normal or?
I cannot manually get inside the Xbox to adjust anything, either.
Covering ANY electronic device could cause harm to the product or the user using it.
When dealing with the Xbox Console in general, it is recommended to have it in an open area or if it's place within a shelving unit give it a 2' X 4' foot spacing around the console so it can properly realease the heat flow from the fan being produced by the hardware.
Also with the 5"(inches) you are currently giving to your console if the room is not AC central (air condition), the Xbox is working through a smog of heat being not only produced by the console but also being contain by the warm/hot climate of the room it's in.
Make these changes and hopefully your Xbox will be back up and running if it's not currently damaged already.
Follow the tips supplied by "Walkie Talkie" but also would not hurt to take a can of air and blow out the fan and inside of the system all around.
It's not normal IMO to cover everything for 9 hours..... Let the system cool down overnight. we can't say if your system is perma damaged or not... The console's lifespan may have been shortened. You seem to know the steps to take. A good rule of thumb is-- let your system cool about 20 min for every 4 hours it's on.... GOOD LUCK!!!
Normally the console should run pretty quiet but there are things that may make it run louder than normal.
1. When loading a disc the fans will speed up and during a game they disc may work the fans more depending on how hard its got to work the graphics
An easy way to prevent this is by downloading the game onto your hard drive from your disc. You console will need to have the disc in to launch the game but it will be much easier on the fans. This like will take you through it
2. Failing that you can check that your console is sitting level as if it is not it will force the fans to work under stress which can cause them to run louder than normal.
3. Finally if the problem still persists it may be the case that you will need to send you console in for a service, If the console is under 12months old the xbox will repair it for free, if not there will be a charge
You can check if you console is under warranty and order your repair through this link