Set mouse speed in windows 10 on startup using powershell and windows scheduler. Speed is in range 1-20 (default: 10).

Win10_SetMouseSpeed.ps1

param([Int32]$Speed=10)

$MethodDefinition = @" 
    [DllImport("user32.dll", EntryPoint = "SystemParametersInfo")] 
    public static extern bool SystemParametersInfo(uint uiAction, uint uiParam, uint pvParam, uint fWinIni); 
"@ 

$User32 = Add-Type -MemberDefinition $MethodDefinition -Name "User32Set" -Namespace Win32Functions -PassThru
$User32::SystemParametersInfo(0x0071,0,$Speed,0) | Out-Null
Set-ItemProperty -Path "HKCU:\Control Panel\Mouse" -Name MouseSensitivity -Value $Speed

Win10_SetMouseSpeed_ShedulerTask.xml

<?xml version="1.0" encoding="UTF-16"?>
<Task version="1.4" xmlns="http://schemas.microsoft.com/windows/2004/02/mit/task">
  <RegistrationInfo>
    <URI>\Win10_SetMouseSpeed</URI>
  </RegistrationInfo>
  <Triggers>
    <LogonTrigger>
      <Enabled>true</Enabled>
    </LogonTrigger>
  </Triggers>
  <Settings>
    <MultipleInstancesPolicy>IgnoreNew</MultipleInstancesPolicy>
    <AllowStartOnDemand>true</AllowStartOnDemand>
    <Enabled>true</Enabled>
    <UseUnifiedSchedulingEngine>true</UseUnifiedSchedulingEngine>
    <ExecutionTimeLimit>PT0S</ExecutionTimeLimit>
  </Settings>
  <Actions>
    <Exec>
      <Command>powershell</Command>
      <Arguments>-windowstyle hidden -file "%USERPROFILE%\Win10_SetMouseSpeed.ps1" -speed 15</Arguments>
    </Exec>
  </Actions>
</Task>