[Draten-Master of Fire and Ice]

I have not gotten to the White Dragon yet, but I have fought and decimated White Dragons before so I have a few ideas you can try.
1. Try to use missile weapons to whittle down on the beastie before it closes to melee range. Order your henchman to do the same.
2. Use your Ranger's entangle spell to make it hold still and take its medicine (from your missile weapons). If the sucker isn't immune to entangle it may have a high spell resistance so it may take a few times for this method to work...saving games rocks!
3. Get anything and everything that provides your character with cold resistance.
4. If your 'ol Red Tiger keeps getting toasted (frozen) then have him use only missile weapons for the entire encounter.
5. Use any and all Wands, Staves, and other limited use items to give your dude the edge. Keep experimenting to find what works, that's what I always do.
6. Party On!!!