dvd rom will read cd but not dvd’s

my cd/dvd rom drive will play cd’s but not dvd’s. I recently ugrgr aded to win xp but I have installed a compatible decoder for windows xp and according the the decoder checker it is compatible with media player 10 which i use. Just a minute ago I recieved a message saying that the dvd drive could not be read and that it wasnt formatted. Is there away to format a dvd drive? If so how should I go about doing this?

Thanks,
Leaundrae