The first way to fix this error is actually really quite simple, it may just be your AV cable. The first thing that you can try is to unplug the AV cable and blow out any dust that may be built up in the connections. Then try hooking it back up and turning it on.
If you are still facing the error than try getting a new AV cable, or you can borrow one from a friend so that you don't buy a new cable if this is not the solution either. Once you have the new AV cable, plug it in, fire up your Xbox 360 and if the error is still occurring then you will have to move on to the next method of fixing the E74 Error.
You can find Xbox 360 repair guides on the Internet that have very detailed instructions on how to fix the E74 error as well as other errors like freezing, the no video problem and the red ring of death. These guides usually come with very detailed step-by-step instructions. The better guides will also include pictures and videos of the process so you can be sure that you will understand each step of the repair.
So if you have experienced the Xbox 360 E74 Error, it is not the end of your gaming days, you can fix it. Hopefully it is just your AV cable but if not there is still a solution out there if you are willing to do a little more research.