I recommend you to:

1- reinstall Windows XP

2- install your latest graphic card drivers

3- install P6 then the content updater

4- install sr3

Do not install anything else before testing that P6 sr3 actually renders in firefly.

I know, it's boring but this will probably work.

Oh, for your test: do not use any scene you already created..

Create a new one with your P6 content.

Do not use any light set but the P6 original ones or create them from scratch.

For the Dry Shaders, do not use more than 1 light: it would be useless and ressource consuming.