Hello, my name is Dan.
I will do my best to help you, the only stupid question is the unasked one.
There are a few reasons this may be happening.
First, the disk may be bad, try a different disk, if that works then I would suspect the disk.
Second, if it spits out the second disk then try a pram reset.
To do a PRAM reset, you need to restart your machine and hold down these 4 keys.
‘Option’, ‘Command (Cloverleaf or Apple)’, ‘R’ and 'P'.
Keep them down until you hear 4 startup chimes, this is the sound that your computer makes when it starts up, it is like a boonngg. The screen should also cycle from white to black and then back to white along with the chimes.
This resets all of the system buses on your computer, USB, FireWire, display, ethernet and your keyboard/mouse/trackpad.
This will correct many faults but not necessarily yours.
Third, you may need a DVD head cleaner, this can be obtained at Wal-Mart, Kmart or most any box store.
If all of the above fail then you will need some service on your MacBook.