I am sure this question has been asked many times but I can not find a relevant thread, as I have only recently moved to Mac from a PC up until now I have used a folder on a USB stick for Photo transfers to my iPhone 3Gs and select this in iTunes for syncing. It has always worked fine except for one issue.
Say the master folder on the USB stick is called iphone Sync then all files and folders within this are sent to the Iphone but with one issue which is duplication.

If I have a sub folder within the master folder called say fun then when synced a new library folder appears on the iPhone called fun which is as it should be re categorisation but the photos within this sub folder also appear in my iPhones photo library thus creating duplicates. I am still beginning and not fully conversant with iPhoto so using my above method is there any way to stop this duplication?

I have started to use iPhoto so am sure once I am confident all will be fine re creating new libraries, but your answers would be of great help to friends who have not seen the light and run PC`s.

Just realised this should have gone into the iPhone forum so can a Mod move, sorry for my mistake.