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using System;
using System.Runtime.InteropServices;

namespace MouseSpeedSwitcher
{
    class Program
    {
        public const UInt32 SPI_SETMOUSESPEED = 0x0071;

        [DllImport("User32.dll")]
        static extern Boolean SystemParametersInfo(
            UInt32 uiAction,
            UInt32 uiParam,
            UInt32 pvParam,
            UInt32 fWinIni);

        static void Main()
        {
            uint Speed = 20; //Wert von 1 - 20
            SystemParametersInfo(SPI_SETMOUSESPEED,0,Speed,0);
        }
    }
}