DVD-ROM not reading DVDS

I had purchased this samsung dvd writer. worked fine for a few days but now it just refuses to work. it simply does not read dvds now.. it is able to read cds though (already had a cd writer so that does not help ) and strangely whenever i put in a dvd it reads it as a blank cd.. am clueless as to what to do about it now.. is the piece faulty.. or is there some s/w that i need to install, to make it work