Despite a number of posts where I have stated what I use for writing (and having stuck to Microsoft Word) I can now reveal that I am looking at Scrivener for Windows. I may have mentioned it before, but it is the Windows version of the Mac software.
It’s still in beta form (currently 0.0.29), but has been coming along nicely and I feel it’s not that far off a release version. I suggest you have a look at it and see if it will meet your needs. The website will give you sufficient details and you can download a version to try yourself.
Note it does not have the same funcionality of the Mac version but again I feel there is a lot there for us Windows users to use.
Form me, I currently have two stories I’m working on (slowly) under Scrivener. I like the way you can break down the story and segment it, so your writing is in segments and the software supports you in what you are trying to do.
I have a number of other ideas I’m going to be fleshing out into multipart stories, so will put them into Scrivener as well.