When I backed up ETM to my HDD, I was using an older version of Avalaunch that supported "long" filenames. I was able to play the game from beginning to end using Ghost with no problems. Didn't play with the other character though, whatever her name was, lost interest. Anyway, idiots, in their infinite wisdom complianed about the long filename support and hounded the Avalaunch team to get rid of it. So, as far as I know, it is no longer there. I could be wrong.
It's the long filenames that cause problems backing up ETM to HDD. If you have a DVD burner, and want to make a perfect copy of the game using a DVD disc, then I suggest you use
Alcohol 120%. I was able to make a perfect working copy of SW:KotOR using the original disc and Alcohol.
Since I have not tried backing up ETM recently, that all the info I can help you with.