Syncing iTunes playlist on Windows PC to iPhone

After you've installed iTunes on your Windows PC (I use Windows 7 Professional) go to your Music folder and inside the iTunes folder create a folder to store all your media for your phone i.e.: Music, Videos, Tones, eBooks 

You can name the folder "Data Store"

Open iTunes and go to the relevant media tab e.g.: Music

Click on File->Add File to Library...

Locate your folder, in this case Data Store and choose the file

Once the file is in your iTunes library you sync your library with your iPhone

The files in my iTunes library are only for syncing with my phone.  I use VLC Media Player for all my media on my PC otherwise.

Connect your iPhone USB data cable.  iTunes will detect your iPhone

In iTunes click on the mobile phone icon (top left)

Under "Settings" on the left-hand-side ensure you have the Sync option selected for your media types

Under "On My Device" on the left-hand-side click on your media type and click "Sync" on the bottom right of the iTunes windows

iTunes will sync the library with the iPhone and the library will always find your files in the Data Store folder (no file missing messages) 

If you want to delete a file simply delete it from the playlist and sync again with your iPhone