There are people on EBay that say they can fix the E74 error and if you do a search on Google you can find a few.
For me, once it gets to E74, it goes in a box with the others. It really needs to have the chip pulled and re-balled. I can't do it and its not cheap to have it done, so in the box it goes. I've only gotten one Xbox 360 to stay working by heating it with a heat gun and I consider that a fluke.