2003 ford winstar is stalling, the belt squeals and something ? Is seizing up and causing the van to stall.

Remove the drive belt and check every accessory pulley, as well as the idler and tensioner pulley.
They should all spin fairly freely, except the power steering pump may be not so freely.
If any don't spin by hand or are making growling noise, replace them. They should have no excessive play or bearing noises.
Also, with the belt off, try running the engine to make certain it isn't stalling anyway.

When is the van stalling out? At any given time or is it only when it's cold/warm?

Rich's advice is also accurate; like he pointed out at the end of his post, something else is probably causing the stalling. I've never seen a seized pulley cause a vehicle to stall... unless of course, the pulley seized on the alternator and the operator kept driving.