Optic drive?

[yamaha81]

So I think the optic drive in my Mac may be broken. I just removed the broken hard drive also. So I need to check and see if the rest of the computer is ok by booting it up off of an osx disk. Will an external disk drive work to do this? It may not be broken though. It put it in the side and it acts like it would load the disk then it makes kind of an odd sound then I just eject the disk. I haven't tried using the osx disk yet just an old burnt cd that I had. The computer was dropped off of my friends car so that's why I am replacing this stuff.I hope that the drive just won't do anything with the music disk because the computer has no hard drive and am hoping that an osx disk will load and boot it up. Then I can continue fixing parts of the computer such as body pieces and a new hard drive and the glass over the screen.