My Xbox is overheating!!!?

My Xbox just gets 2 red rings. I searched google and I found out that it means that's it's overheating. So I let it cool down for about 4-5 hours and get back on to play and it works for about 5 minutes and then it shuts off again. I was told to get it off the carpet so I did but it still won't work. I put about 5 psp cases under the xbox so it doesent over heat on my stand but nothing. Does any one know any tips or tricks I can do to prevent it. Also sometimes I try to play and it worked for about 2 hours then I think it's been fixed but the next day I have the same problem. Can anyone help me?