I have a 2004 Grand Prix, and the headlight on the passenger side was almost opaque. On the driver's side, it showed some sign of spider web cracks.

Since my vehicle has only 44,000 miles, I took it to a Pontiac dealer. They went to GM about it, and I got 2 new headlights under warrenty.

I think that there are some defective headlights installed in 2004 Grand Prix's and GM is aware of the problem, but you have to complain to get it fixed.