Solution 1:

You can edit this file:

C:\PowerShell\Modules\Microsoft.PowerShell.Management\Microsoft.PowerShell.Management.psd1

Just comment out this line, or remove it:

"Stop-Computer",

You wont be able to shut down with PowerShell, but I dont think I have ever wanted or needed to do that. You can just push the power button on your computer, or shut down from the Start Menu.