iPhone 4 Still Won't Sync to Dell Laptop

Since I updated iTunes the last time, iTunes doesn't recognize my iPhone 4 or my iPad 3 when I try to sync with my Dell laptop. I never had any problem before updating both iTunes and the IOS on the same day.

I've now updated my iPhone software to IOS 7.1, but that didn't make any different. The laptop recognizes the iPhone, but iTunes does not.

I've tried the fixes shown here, such as checking whether the Apple Device is installed, but nothing shown so far works.

Is there a bug in the latest iTunes?