I've been trying to fix this xbox for a while now. I've looked around for problems similar to mine, but none suffer from all of the same symptoms.
1. This xbox used to scratch discs. I was going to replace the drive, but found the problem and fixed it instead. The magnet had come loose and was stuck to the inner case of the drive. I fixed this and my system no longer scratched discs.
2. After installing the newest 8/11 update, the system booted up into an E71. I held the sync button and all was well. The system booted. However, my drive will no longer read discs. Well, that is, it won't play games. It will play audio CDs. It also seems to read the games, because I can save them to my hard drive. When I try to play them afterwards, though, it says that it can't play the game, and I should reinstall it. I've done this to no avail. I'm presented with the same error.
3. As if this isn't enough, I'm never able to play any new games, even if eventually I fix the read problems, because my system simply won't update. Every time I attempt to install the update, I am presented with a wonderful E71 error again.
4. But wait, there's more. I will be cruising though my dashboard, seeing what else an xbox does besides game play, and it will freeze. Sometimes it gives me 5 minutes from boot, sometimes 5 seconds.
I do have some theories as to why these things are happening, but I just don't know how to go about fixing them. The fact that I am unable to update, have constant freezing, and can install games but not play them, leads me to believe that I have serious problems on a software level. However, it could all be related somehow to a faulty dvd drive and replacing it could solve some problems. I do have another dvd drive from an old xbox available, but, as I have no good computer to hook it up to, it would be a mighty pain in the ass. Running my laptop off of a windows 7 bootable flash drive and having my xbox drive protruding from the bottom while trying to get the key off of it could be possible, but I'd like to avoid that.
Sorry for the long post, but I figured the more information the better.
Any ideas from the experienced pros that this site possesses would be greatly appreciated.