The best way to fix the E74 error is to get a replacement or have it repaired. Unless your 360 is still under warranty, those approaches will cost you a lot of money. Below are some alternative solutions.
Required Tools and Materials
Clean dry piece of cloth
Can of compressed air
Shut down the 360. Disconnect the controllers and cables. Disconnect and remove the hard drive and other components. If you have any DVD peripherals, remove them too.
One of the possible causes of E74 is a faulty connection. Take the 360 to another room. Place it on an even surface. Plug in the cables and power supply to a working electrical power outlet.
Turn the 360 on. If the error message disappears, the problem was the connection. If the message is still there, proceed to step 3.
Turn off the Xbox. Remove all the cables. Use the can of compressed air to clean the cables. Wipe the cables with a clean piece of dry cloth to remove persistent dirt. Reconnect the cables and turn the unit on again. Go to step 4 if the problem persists.
Another way to fix the E74 error is to get new cables. Turn the 360 off and check the cables. Are they worn or bent? If so, you need to get new ones. Once you get the new cables, plug them in. This should remove the error message. If there is still an error, try the following.
Remove the hard drive and any game disc inside the 360.
Hook up the power supply and AV cord. Power up the 360.
When the E74 error message appears, remove the AV cable. Get four towels and wrap them around the 360. Leave the towels on the unit for 45 minutes.
Take the towels off. There will be a couple of red lights blinking. Let the console cool for half an hour. Make sure the hard drive is not connected to it. There should be no cords or towels on it either.
Plug in the AV to the television. Reconnect the power supply. Install the hard drive. Turn the console on. The error message will no longer be there. If the error reoccurs, repeat the steps.
The towel trick, as it is called, should only be used as a last resort. Use the other methods to fix the E74 error before trying that one.