To completely disable User Account Control on a Windows machine set the following registry key.
Key: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
Value: "EnableLUA"
Type: REG_DWORD
Value: 0x00000000
The following powershell command does the trick nicely:
Set-ItemProperty -Path registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System -Name EnableLUA -Value 0
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