My PC's DVD RW drive reads movies but somehow lost the capacity to read backup data

[Gesnarf]

DVDs? Instead, it does a search in My Documents and "finds" a little txt file called desktop.ini. Sometimes, it thinks it's seeing a blank disk and asks me to add files (which I, of course, can't), or simply crashes.

Help!

The data disks are undamaged and I've copied files from them very often. I have a Dell Inspiron 530 Core Duo with lots of memory running on Vista.