Loud squeal; car dies while driving

Hi there!

Yesterday I was driving approximately 50-60km/h when all of a sudden the check engine light appeared and the interior dash lights started to dim and then the car lost power and came to a full stop - al within about 15seconds. I tried to start the car again and nothing, it wouldn't even turn over. For the last few weeks - everytime I start my car there is a very loud squeaking noise coming from the engine area (perhaps a belt). The sound usually continues for a few minutes, and then stops completely. This is the first time the car has completely lost power like this. Could this be my alternator, battery, or maybe even main relay (i had it re-soldered a year ago and was told it could go at anytime)? I checked the belt and it seems tight.

Thanks!