Open Task Manager (Ctrl + Shift + Esc)
Click File - Run new task
Tick the box marked 'Create this task with administrative privileges'
Type powershell into the box and click OK
Paste this command into Powershell and hit Enter
Get-AppxPackage Microsoft.Windows.ShellExperienceHost | reset-AppxPackage
Paste this command into Powershell and hit Enter
Get-AppxPackage Microsoft.Windows.StartMenuExperienceHost | reset-AppxPackage
Close PowerShell and restart (not shut down) the PC.