I have a laptop and desktop I originally setup my iphone on my laptop, i have the Sync options under the 'summary' tab unchecked in itunes and checked the 'manually manage music and videos'. When i plugged it into my desktop, i could not drag/drop music to it. the 'manually manage...' option was not checked, so i checked it. I then recieved a message saying: The iphone is synced with another itunes library on "laptop name". Do you want to erase this iphone and sync with this itunes library? An iphone can be synced with only one itunes library at a time. Erasing and syncing replaces the contents of this iphone with the contents of this itunes library." So i hit cancel, but whats the deal, i unchcked every 'sync' option i could find on the laptop.