Why do itunes do this?

[johnniearchangel]

when syncing songs from my pc to itunes, i do get this error: was not copied to iphone because it could not be found or wont even get the error, and it still wont sync all songs.

in the attached image, you could see sync music is 1044 but the actual songs i want it to sync is 1200...pls any solution to this?

 

[Tartarus]

The songs that weren’t synced couldn’t be found on the computer.
Make sure the songs in iTunes are also on your hard drive.