iTunes questions

A friend asked me to reinstall Windows on her laptop. Using Vaio's F10
recovery option, the D: partition remained with all the iTunes music
files intact. C: partition is where a fresh installation of Windows
resides.

I downloaded the latest version of iTunes for Windows. I installed the
program on C: but I later went into Preferences to change the location
of the music directory, pointing it to the D: drive (specifically
D:\iTunes Music). But when iTunes shows files in the main window, it
instead uses the default files, found here:

C:\Documents and Settings\Sarah\My Documents\My Music\iTunes\iTunes
Music

What is the proper way to consolidate everything?

Also, any recommendations to make Windows run more lean, with regard
specifically to iTunes? I noticed the following startup
programs/processes:

iTunesHelper
Apple Mobile Device
Bonjour Service
iPod Service

I suppose I could just disable them all, but I'd like advice from
someone with experience with iTunes, preferably.

TIA.