You need to run the PW2 translation utility on your file before opening and saving. Even then the materials really don't look the same in PW2 as they did in PW1. I found it's best to just re-apply new materials in PW2.
Ah.. Custom materials won't translate at all!!! You will definately need to re-apply those. Welcome to PW2. In all fairness PW2 does produce a better rendering. It is a bit of a shock when you realize your old renderings all have to be redone.