Windows 7 DVD rom detects dvd but doesn't detects media!!! Need Help !!!

[nirvana]

I have Sony Vaio VGN-NW-23NE with windows7 Home Basic(64-bit). Few days back i got it recovered as it was crashing frequently, after that my dvd drive won't play any media though it detects that a DVD has been inserted but it shows it blank. I have tried with all type of DVDs but the result is same

Please help me on this my lots of data is on DVDs as i made back up on it before restoring it