Apple Hardware Test does not work on my Mac Pro for some reasons. Maybe it's because I did some fresh installs of Yosemite before. And it maybe deleted the Apple Hardware Test. I have 10.6.8 (which the mac came with) on some DVDs, but don't want to install it. But the AHT should be on those DVDs. I also got the AHT on another DVD from someone. It's the AHT which is made specifically for my Mac Pro 5,1. But I couldn't install it, because it said it was too old. So I called apple, and they sent me an update of El Capitan, the latest one, but it's a "Combo Update". (Whatever that means) So apparently it's different than the standard update. They told me the AHT for my Mac would be included in there. I tried to run the test. Didn't work. Anyone know what to do? I really need to run the test. Thanks!