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#21
I recall having this same dilemna and after not finding the setting, interfering program, corruption, etc. responsible ran a Repair Install which by reinstalling the OS fixed the issue. However there are some bad settings it will not set right.
That said if this is just one of several issues you have which are causing WIn7 to not run perfectly you might consider taking the time to get a perfect Clean Reinstall - Factory OEM Windows 7 using the tools and methods which work best, then capture an image to use if it ever becomes irreparable again.