age/appearance of belt-does it look like it could use to be replaced?
have you tried to adjust the tension?
my 98 would make a soft squeek when 1st started and louder if i had the 'defrost' on but once it warmed up it would go away. tried a shot of mobile1 on pullys(works great on trailer slide outs), bought new belt(twice-wrong one 1st time-take size/number to parts store, save a return trip), then went nuts trying to figure out the belt adjustor. tightened and no more noise and have new belt for when it (really) needs it.