My mistake... Step 8 should have read:
Close iTunes. Rename the folder D:\My Music as D:\iTunes. Hold down shift as you start iTunes and open D:\iTunes\iTunes Library.itl. Check that files play normally. Confirm under Edit > Preferences > Advanced that the media folder is now given as D:\iTunes\iTunes Media, if not correct then close and reopen iTunes.
Sorry for the confusion/added stress. 😕
You should probably use File > Library > Add folder to library and select D:\iTunes\iTunes Media to add in any tracks that are in the media folders but not connected to the library.
The DeDuper script should help clean any dupes.
If you've got any inconsistencies in the naming of albums or bands the tracks may be spread across multiple folders. The article Grouping tracks into albums gives details of how to tidy up. As you correct things in iTunes it should reorganize the media to reflect the changes.
If Windows Media Player has ever been connected to your for files then there will be artwork spread around. When iTunes moves files about it leaves these behind so you can have folders containing a bunch of hidden images and nothing else. The script CleanDeadArt can help here.
tt2