.MSEInstall.exe /s /runwgacheck /o
Start-Sleep 5 # I have no idea how to wait for the installer to finish
Set-ItemProperty "HKLM:SOFTWAREMicrosoftMicrosoft AntimalwareScan"
ScheduleDay "0"

Set-ItemProperty : Requested registry access is not allowed.

$user = whoami
$regPath = "SOFTWAREMicrosoftMicrosoft AntimalwareScan"
$key = [Microsoft.Win32.Registry]::LocalMachine.OpenSubKey($regPath, [Microsoft.Win32.RegistryKeyPermissionCheck]::ReadWriteSubTree,[System.Security.AccessControl.RegistryRights]::ChangePermissions)
$acl = $key.GetAccessControl()
$rule = New-Object System.Security.AccessControl.RegistryAccessRule ($user,"FullControl","Allow")
$acl.SetAccessRule($rule)
$key.SetAccessControl($acl)

Exception calling "OpenSubKey" with "3" argument(s): "Requested registry access is not allowed.