Dafydd.
I have a brand new computer (Lenovo G50) that won't start Windows Explorer automatically (i.e., no desktop on start up). If I bring up the task manager, I can run explorer.exe, but as soon as I restart/log off, I have the same issue.
I've run scf/scannow and no issues are found. I've also ensured that the shell in the registry is called explorer.exe. Virus/malware scans come back fine. I don't have this issue in safe mode. Any ideas to get it to run on start up without forcing it to run a new task each time?

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