Sounds like a bad burner to me. My DVD combo drive used to burn a cd good, then it would complete say an mix of songs and only the first four were playable, this started happening even though Nero said it was completed. Now the drive craps out after about 3%, so maybe try a new burner (they're cheap anyways now). Also are your ISO's good? where did you acquire them? Can someone else burn the same ISO from another computer ect... If i remember right I had heard of someone replacing the CDROM with another one a 4X speed one, but I'd have to hunt back into my saved stuff to find the article and what drive it was (a NEC I believe). Heck I never tried so not sure it would work either