My mom's 2005 Xa headlights wont come on.

Regardless of prior testing - this TEST needs to be performed.. IF unfamiliar with how to TEST fuses - seek *hands-on* help from qualified personnel. Good luck!

Thanks. As stated, the fuses are good. They all tested out fine. This is something deeper. Any other thoughts that would explain it?

I have the dimmer switch out and it seems to be testing fine with respect to continuity as well. This is why I'm curious about the computer operation.

Ohm test BOTH of the bulbs! Check for power and ground at headlight wire connector. Use Google - may find a free - downloadable schematic online.