My dvd -rw wont play any movies

i have a packard bell pc had it bout 2 yrs or so now an other day i put my tiscali broadband cd in 2 the dvd drive an it played thro nero 7 by mistake an wen i went 2 play a movie on my dvd it wouldnt pick up its as tho its tryin 2 pick up then failin as i can hear it goin round then stoppin the sound also went off but i got that workin again now just wondered if any1 knows wat the prob could be it said something bout a (class installer registry entry is invalid) but i dont know if this is still the prob as i got my sound workin does any1 know wat it could be as i just cant play any dvd’s on my dvd rw thanks any1 help :sad: