Dvd writer problem writing only cds wat do to

Hello,



I HAVE LG DVD RW NOT READING DVDS BUT READING ALL CDS. VERYVERYLONG GAP ONCE THE DVD MAY BE READS. I HAVE CLEAN MY DUST IN MY CPU AND DVD RW . THE SYSTEM WORKING WITH WINDOW XP OPERATING AND ALSO HAVING SPEED. ONLY THE PROBLEM IS NOT READING MY DVDS. PLEASE GIVE THE SOLUTION, I HAVE READ THE PROBLEMS INTHESE SITE BUT NOT IN USE.