This morning i noticed that my dvd rw werent reading discs it was fine a cpl days ago and nothing has happened since then - does anyone know what the prob could be

Does anything come up on screen, any error messages. It sounds like the laser may have came out of place. But just to check give the discs a good clean.

na - i noticed it wen quickly checkin dvd decrypter it said medium not present so i put in 3 or four more discs to no avail - what can i do if the lens was knocked

Have you got any other DVD drives you could try putting in your current PC and testing whether the same discs work?

Another drive in the comp read one i tried

Well that suggests it is the drive playing up then, are you sure the drivers/firmware is updated and installed, also check it is properly plugged into the motherbaord. If you are not sure, tell me the make and model of your pc or the make and model of the drive.

thanks