Dvd burner wont play dvds



im new to this forum but i really need some help and i found some good stuff on this site before so i desided to try it out.

alright, all of a suddend my dvd burner stoped playing dvds. its really wierd because it use too. it still reads cd like normal, but when i put in a dvd it just cant read it.

ive tried a few things: i tryed 3 different dvds, i checked if the plugs were pluged in, and i went though the trouble shooting guide.

the dvd burner is Sony DVD RW DW-U12A
im running XP home
i use power dvd
p4 2.66 processor
512mb of ram

i cant figure it out. help me out guys