Just what version of iTunes do you have? For a 5G iPod/iOS 7 you need iTunes 11.1 or later.. If you have a Mac yo need OSX 10.6.8 or later.
Does the iTunes still see the 4G iPod?
- I would start with
However, after your remove the Apple software components also remove the iCloud Control Panel via Windows Programs and Features app in the Window Control Panel. Then reinstall all the Apple software components
- New cable and different USB port
- Run this and see if the results help with determine the cause
- Try on another computer to help determine if computer or iPod problem