I didn't see any posts on this here but this is a great fix for older Xbox's with overheating issues which usually prompts the 3 Red Lights or E74 error. There is a great kit made by Team Xecuter that helps not only repair most of these related issues but also reinforces better heat protection. It also replaces the current clamps to the heat sinks with one solid universal clamp system that locks in the heat sinks better to the GPU and CPU also. Take a look at the link below to see what is involved and always be careful when performing this repair. Also this kit when ordered comes with all the easy tools you will need to perform the opening of the Xbox and clamp removal with ease. Also highly recommended to use Arctic Silver thermal paste instead of normal replacement for better treatment. Another thing to help with your system, if you have 1st generation heat sinks for the GPU and CPU, be sure to replace them with 2nd generation heat sinks as they offer more protection and are built better to suit your needs.
These can be easily obtained on EBay and are fairly cheap and usually have free shipping on them.
How to open Xbox -
How to install The Extreme Repair Kit -
WARNING - IF YOU HAVE TRIED THE TOWEL TRICK AND BAKED YOUR XBOX BEYOND BELIEF YOUR XBOX MAY BE BEYOND THIS REPAIR AND MAY HAVE PERMANENTLY DAMAGED THE GPU OR CPU ALREADY!!!
Be careful when performing this procedure as you could do permanent damage to your Xbox. I do not accept any responsibility as to what you use with this information. If you do not feel comfortable performing this task please seek a professional who can do this for you.