well the problem is that your ac compressor is locked up and when you turn the ac on it engages the comperssor clutch causing the belt
to "slide" on the pully causing the smoke. caution on the neon the ac belt also runs the p/s pump if you destroy the belt you will be without power stering.
as safty goes just dont use the ac and if you live in a place were it gets cold and you turn the front window defroster on you will have to disconect the ac clutch wire witch is located on the front of the engine on the ac compressor.
i hope i have helped you out
