I recently ran into this problem of iTunes NOT seeing my iPhone or iPad, even though Windows 8 recognized it with no problem.
Well, come to find out, somehow the "Apple Mobile Device USB Driver" drivers got uninstalled and only Microsoft Windows 8 drivers "Portable Devices" MTP USB Device driver existed.
- Right-click on "This PC" or "My Computer" and select "Manage". This will bring up the Computer Management windows.
- Now, click on "Device Manager" and then expand "Portable Devices"
- Right click on "Apple iPhone" and/or "Apple iPad" (make sure at least one of these are plugged in) and select "Update Driver Software"
- Select "Browse my computer for driver software"
Copy/Paste this path into the "Search for drivers software in this location" field:
C:\Program Files\Common Files\Apple\Mobile Device Support
- Now hit "Next", and you should be done!
iTunes should now see your Apple iPhone or iPad.
If that still doesn't work, then simply uninstall ALL iTunes related apps:
- Apple Application Support
- Apple Mobile Device Support
- Apple Software Update
Then re-install iTunes.
Note: Your music and settings should all still be fine, the uninstall above doesn't delete any of that.