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Most of us here, including myself, are not having problems, but choose to use Auslogics, we feel it is faster and more through.
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If you do not care to go this route, go back with a system restore and then we decide what to do with your Norton.
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I agree with Rich that Auslogics makes a more robust defragging program than the limited functionality version provided by Microsoft by default. However, the original defragger should run and if it cannot it may point to other problems afoot. I'd at least try to do a little troubleshooting to rectify the problem.

The program that should run is "windows\system32\dfrgui.exe". I'm assuming the file is still there, because if you clicked on the program link that points to a missing file, you'd get a "file not found" error. So, there may be a dependency (like a dll) this program relies upon that is either missing or compromised.

Just to be sure your core system is OK, I'd follow the SFC scannow tutorial. If this doesn't help, then it may be prudent to roll back to an earlier restore point, before you installed Norton 360, and verify that the defragger is operational.