First:
iTunes: Fix iPhone or iPod Not Detected in Windows 10
next try
Apple Mobile Device USB Driver Missing
last
iPhone, iPad, or iPod not recognized in iTunes for Windows
- I would start with
Removing and Reinstalling iTunes, QuickTime, and other software components for Windows XP
or
Remove and reinstall iTunes and related software components for Windows 7 and later
- New cable and different USB port
Also see:
iPod not recognised by windows iTunes - ASC
Troubleshooting issues with iTunes for Windows updates
- Try on another computer to help determine if computer or iPod problem
Note that some links may not work because of a temporary problem with this forum