First of all, if you were ONLY installing Evox WTF did you take the HDD out for, or for that matter why did you even open the box?
If you have a back up IMAGE (a bin file type back up), hot swap the HDD to your comp & restore it. From my exp you can use a bin file back up from ANY xbox on ANY other xbox (I may be wrong for newer boxes).
If you can't even boot a game this is most likely your only hope.
If you don't have one from your friends xbox, make one from yours, then restore that one to your friends xbox.
Find the HDD tool in the usual places, this will do what you need.
I don't understand why you people don't use the UDE, it's as simple as installing a game on your computer.
to make sure you know what you are doing.
Sorry if I come off as a dick, but you should really know what you are doing before you take someone elses shit, & fuck it up.