did you also check the inside pads? the slide pins froze in my rear caliper and i couldnt figure out what this wierd sound was... outside pads looked fine but inside was completely gone and was metal to metal. lucklily i cought it b4 it did any damage to the rotors
Try adjusting your emergency brake cable. I am almost positive that my friend with a 99 had to do this because his car was squeaking like crazy. That was like 4 years ago though so my memory could be off ..
I also just read that it could be a "loose e-brake cable bracket"