[mountainlion]

You can add an external drive quite easily. Do you have enough room on the mother board to add one? There are probably many websites to give step by step details on how to do this. The Public Libraries probably have many books on this. Choose the most satisfactory method for you.

[DGHoodini]

I agree woth mountainlion. The best option, IMO, is to get a USB external rewritable DVD drive. Then all you have to do, is plug it into an open USB port. Assuming you have the required HW & OS.