Now why did you go and buy a Pyle DVD player??? //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif
Lets see, you put a ground loop isolator on and regrounded the unit, thats the first thing I would have suggested.
If possible, remove the head unit from the car and bench test it, if the noise persists on the test bench then somthing is faulty in the unit.
Does the noise only happen when the car is running?, or is it present at all times?.