Did your car do that all winter? Wouldn't moisture on the belt just last for that one time and then dry up and not happen again?
I don't know if this will help anyone hear what's going on with my engine when it starts cold (or if this is the same kind of noise anyone else has heard), but here's an mp3 of it (inside the car, doors closed). The high-pitched start, a rev with the high-pitch, and a small rev at the end which sounds completely normal. (SparkYZ, this the same kind of noise your cars were making?)
http://members.shaw.ca/raubt/mustang_cold_rev.mp3