Might be a strange question, but do you have to keep all songs on your PC for them to be on your iPhone?
For example if you had 300 songs it would take up a hell of a lot of space on your computer. Once they are on your iPhone can you delete them off your computer?
The reason I ask is because I had a song on my computer which I put on my phone. I then deleted from my PC and the next time I plugged in my iPhone it sync'd automatically, but came up with an error saying it couldn't find the song.
I have just ordered an iPod Classic too and wanted to put my whole CD collection on it.