Replaced HDD Now will not Play DVD's

Last October I had to replace the Hard Drive on my Inspiron 600m. I had to pay Dell $50 to send me the drivers and other system software which came with phone support. I now discovered I cannot play DVDs on the lap top. I believe this has to do with either a driver or lack of DVD software problem. I have not tried to play a DVD until toady but need that capability for my business. Does anyone have any suggestions?