With Snow Leopard (OS 10.6.8), a program called DVD player is included. When you insert a CD or DVD into the drive, does it show up at all on the desktop? Also, after putting in the media, when you launch the DVD player program, does it recognize what is in the drive?
By the way, after inserting the DVD into the drive, how do you get it out?
The other thing to try is in the upper left hand corner, there is a black apple. When you click on that,a sub-menu appears, and the first entry says "About This Mac...". Click on that, and on the next screen you should see a "selection" called "System Report". Click on that, and on the next screen, within the left hand column, you should see an entry called something like either DVD drive or Disc Burning (I use OS 10.10.2, and it says Disc Burning. Can't remember what it says with OS 10.6.8). Click on that, and something should appear that has information about the DVD (Super) drive. If there is nothing, then the drive might be defective in some way.