Well just bought HoW today, and I'm about 3/4 through IWD. HoW can either be started by importing the IWD final save, or by going through a door in game in IWD. However this door is some way into IWD, so you can't start HoW in HoF mode form in game, as far as I know. Someone whose a little further ahead should be able to clarify this.
------------------
Holy Avenger of the OHF
HATS for sale baby!
Sponsored by Yorick
Your ad here? Call 112 -221 -123