It would help to fill out your vehicle's profile.
Seriously, it can be dozens of things. There are some things that people recommend all the time (fuel pump, crankcase position sensor, and PCM), but it could be one of three dozen things.
Before you start throwing parts at the problem, three questions:
(1) When you say you replaced the computer, was it remanufactured, a used junkyard or eBay item, or from one of those dealers that cleans and polishes the exterior and then resells?
(2) A stall or no start is caused by no/low fuel, no/intermittent spark, timing, or mechanical issues. What testing have you done?
(3) What repairs have you tried other than the PCM? And, what parts did you use in the repair?