Crankshaft Pulley Bolt missing

Remove the pulley and make sure the holes have not elongated from being run loose. This could be your belt squeeling problem but here is a short list of other things that can cause it.
1. belt wore out
2. Pulley groove worn, letting the belt bottom out.
3. Painted pulley groove (takes a long time to wear off paint)
4. belt loose
5. wrong width belt
6. pulley alignment