ADCIN doesn't work with port pin aliases. Use ADCIN 2,W0, or define PinProbe as a constant. PinProbe CON 2 would work.

Also ADCIN doesn't setup TRIS, ANSEL or ADCON1. So you end up with Fosc/2 for your A/D clock because ADCON1 defaults to all 0's. So you're way out of spec for a 4MHz osc. Fosc/8 would be a good one to use with 4MHz (see datasheet).