Unplug the cable that connects your device and your computer from the current USB port, and plug it into another one. Believe it or not, this step solved the problem many times.
Restart your iPhone and your computer.
Update your antivirus software.
Uninstall all software that is Apple-related, such as:
- Apple Mobile Device Support
- Apple Software Update
- Quick Time
When you are done, restart your computer, and install iTunes again.