Disc not being read?

Hi all, I purchased the PMDG  737NGX around February time of 2013 and enjoyed the realistic flying up until now. I have needed to reinstall FSX due to a PC related problem. I reinstalled FSX and all addons except from the NGX. I have the NGX on disc and every time i put the disc into my DVD drive it won't read it. i had a look at the disc and I do not see many scratches, only some very small ones. Is there anything I could do?

Any help always appreciated, Robbie.