The location of the backup files from iTune
It depends on the computer's operating system:
\Documents and Settings\(username)\Application Data\Apple Computer\MobileSync\Backup\
Windows Vista and Windows 7:
Note: To quickly access the AppData folder, click Start. In the search bar, type %appdata% and press the Return key.
To extract files in the backup
Use the iPhone Backup Extractor software. It has a free edition which I find is sufficient for most need.