It may indeed be your xbox mate but then again it could be a faulty ISO

its not the iso because it works on my other xbox and my friends but not my slim how could i fix this?

This is down to the xbox laser, the problem with hotswapping is that being exposed to the air damages the laser thats why you have that foam around the disk driver before you opened it and the light also counter-acts the laser

i would try a dark room if not you could always flash your other xbox's drive so its got the same drive key as the slim and then install it offline then put your normal drive back in but im not sure that will work because never tried phat drive in a slim

i reaaly dont wanna flash it to much effort but is there any think else i can do for laser except trying it in a dark room?

TTG_Hazz wrote i use a slim xbox and this is the one i use all the time when installing iso disc it fails around the 70% mark where on my banned xbox elite it installs to 100% no problem i have tried it loads on the slim and it always fails from 50-75% mark? is it my xbox?

do you need to mod your xbox to get a iso to work or not can i just buy and play?