DVD CD writer problem
 

I have a Compaq computer and replaced a Lite-On Model DH-20A3P with a Sony
DRU840A rewritable drive. It does not recognize that there is a either a
blank disc or one with pics on it. We are using Nero but I am a novice. The
reason for the replace is because the door was jammed and could not get it to
go back in. It did work great before that. Now we cannot burn anything.
The drive does rip music and it shows that it is working. What step am I
missing? We have already spent $250. on this and would like to avoid any
more spending. Thanks. Pat