my Xbox 360 Has a Red Light

If you have been unfortunate enough to have had the red light of death don't worry you are not alone. It happened to me recently halfway through a game of call of duty. I have to say I was not impressed. The RROD is the way the Xbox 360 lets us know that there is an issue to be fixed. The number of lights being displayed also lets us know specifically what is wrong.
One red light is the console's way of telling us that there is a hardware failure. Now this can be a number of things such as an error with the disc drive or the hard drive is not attached properly. To narrow it down the Xbox will display an error code on your display to let you know exactly what is wrong. The error code begins with an "E" and is normally followed by two numbers. E74 is a common example which refers to an issue with a cable.
Two red lights are displayed when the console is overheating. Turn the Xbox off immediately and leave for about 1 hour to cool down enough and you should be good to go. You should take a look for the reason this is happening though or you could be experiencing it again very shortly. Check that the vents can get enough air, they should not be blocked by dust or something similar. Anything that obstructs cool air getting to your console will cause the rrod error for overheating.
Three red lights is particularly nasty as this is the one that normally means your console has to be sent off for repair. The error means that your console has suffered a general hardware failure. This is mostly caused by solder on the circuit board becoming brittle and breaking which results in the error.

Four red lights is caused by your a/v cable not being inserted correctly and can be fixed simply by ensuring that it is connected properly. If you use an hdmi cable you should not see this particular rrod.

As I mentioned you may have to send your console back to Microsoft for repair at your expense unless your machine is under warranty. You will not have your Xbox for about 6 weeks as they carry out the repair too. If this is something that you do not want to have to do then you could fix the problems yourself. My only recommendation is that you use a repair guide unless you know what you are doing as you do not want to cause more problems than you already have.