I got dell desktop with cdrom and dvdwrite bothe were working under vista o/s and when I upgraded to windows 7 cdrom and dvd wite not reading why/ please help.

Are you saying that when you insert a written dvd nothing happens? (autoplay may be turned off). As for writing, what application do you have installed to do the writing to the blank disk? Win 7's disk burning is not so intuitive. There are a few good free burners out there, just search for "best free optical disk burners". For the most part DVD and CD optical drives do not need drivers, windows usually uses their generic ones just fine. But to be sure, you can look on Dells site for your specific model number to see if there are drivers for the optical drives.