In that case, you will need either to unplug another device using a serial connector or add a Serial Port Card. You will have to use a diagnostic program like Microsoft Diagnostics or Norton Utilities to determine what IRQ's are available. Some problems and their solutions are outlined below. Serial Ports in Use Unplug the external modem or mouse to make a port available. If you are using an external modem, it is very easy to unplug the modem and plug in the communications cable.
Some users employ a switch box.
On some systems, these can be switched off to allow the COM2 connection to be activated. Check the hardware documentation for your laptop for details. Unplug the Network Connection On systems which have a network connection attached to a COM port connector, you may be able to disable the network software and remove the connection in order to plug in the serial communications cable. Check with your system administrator. You may then be able to use COM1 for your communications software if your modem is not powered on while communications is in progress.