dvd rw is really a cd burner

I bought my dvd burner and it can't read anything DVD but as a cd rom its great.  For a short while it did play a few DVD movies but stopped soon after!  Whats the deal?  Its like this in Linux and Windows XP its a Digital research DDVDRW8DB
It didn't come with Pinnacle Instant CD/DVD SE like it has on the back of the box so I had to pirate it.  I paid for it so I saw no reason not to.

i had a cd burner that would not burn cds unless there were two jumpers on the master/slave/cable-select pins. 

if you changed the jumpers around maybe your problem lies here.