i dont know whether it sis hardware problem or software problem . the problem is ... My DVD writer is SONY DRU-810A (DLDR & RW) OS-Windows -SP2-connected to net &updated time to time. i started buying digit from december.till february edition theres no problem.my march DVD when inserted in my writer gave message that "windows cannot read from the disk .the disk might be corrupted or it could be using a format that is not compatible with windows".then i send it to digit & got it relplaced.but i got the same message once again.same thing happened with APRIL issue.even that DVD when replaced gave the same result.on my complaint DIGIT send my march DVD once again.but even that was not working.for some reason i reinstalled my operating system.this time i found most of those disks working.but after few days when i tried april DVD for a software then once again i got the same message.then i tested with all those earlier DVDs .i got same result.adding to my frustation even the FEB DVD also gave same message. but this months(MAY) DVD is working fine all the time. i checked other DVDs such as my own written ones , TERMINATOR DVD,DECEMBER one .they all are working i am unable to sort out the problem.plz help me.