My 96 Windstart has a rattling from the bottom of the vehicle. It is really loud when in 1st hear or going slowly after letting off gas. My hubby says it is the exhaust, and maybe it has a screw loose or something. Can anyone help me?

A rattle can be tough to track down.....
If you have the plastic wheel covers.....the tabs are notorious for snapping off....and then the wheel cover will rattle.

The heat shields on the catalytic converters can come loose and rattle.....the FORD fix for that is a oversized hose clamp......2 of them on each catalytic converter.
I have shown this in my pictures.
I got the hose clamps from the plumbing department at the hardware store, big box store (Home Depot, Lowes, etc).

Then, as I had happen, the insides can come loose inside the catalytic converter(s).....and rattle....the only fix for that is to replace the catalytic converter (expensive and a pain).

I also had a rattle come from a small metal shield that is on the "bell housing" transmission......where it meets the engine.....it goes up in between the motor and the transmission...right by the engine oil pan....and a screw can work loose and cause the metal shield to rattle.

There are many other things that can rattle as well.

I would, if you have ramps, get under the vehicle and look around....and check the things that I mentioned.....if it is not a wheel cover.