Hi Tarfhead, just a few more details on this.
The original PC will never be used again and it's always going to be connected to the new PC?
Is it just music he's concerned of transferring over?
A way to lessen it is to set up iTunes homesharing on the original PC and then connect the new PC to connect to the original itunes. That way you can access all the music on the orignal PC and put it back onto the iPhone.
However, the iphone will only sync with one PC, so there will be lost data unless careful with contacts, photos etc.