The iTunes location will be in the System drive (C:) after install. Here we are going to keep iTunes library in another drive (Data Drive) :
1- Open iTunes -> Edit menu -> Preferences -> Advanced tab
2- Check the box "Keep iTunes Media folder organized"
3- Click Change... button to change the location
4- Click OK button (The iTunes will ask you if you want to continue matching the "Keep iTunes Media folder organized" preference, Choose Yes)
5- Go to File menu -> Library -> Organize Library...
6. Check the "Consolidate files" box then click OK
This will copy all of your files over to the new location, keeping your library structure completely intact.