If you have successfully flashed the firmware from Arduino IDE to the Mega2560 then that baud rate and COM port must be the correct ones. I have had issues previously with Repetier Host refusing to connect. Have you tried Pronterface as the host? It seems much more forgiving of differing set ups. It should at least get you to a point where commands can be sent to your machine
As a double check right click My Computer and select Manage from there select Device Manager and open the COM Ports with your Arduino connected you should see an entry for it and the COM port that Windows has allocated to it. COM1 doesn't sound right. Windows normally reserves 1, 2, 3 & 4 for hardware COM ports
As a double check right click My Computer and select Manage from there select Device Manager and open the COM Ports with your Arduino connected you should see an entry for it and the COM port that Windows has allocated to it. COM1 doesn't sound right. Windows normally reserves 1, 2, 3 & 4 for hardware COM ports