How to Troubleshoot COM 1 in XP

1. Click "Start" and "Control Panel" and select "Performance and Maintenance" from the categories, then choose "System" from the menu.
2. Go the Hardware tab and click "Device Manager." Click the "+" next to Ports (COM & LPT), then double-click "Communications Port (COM1)."
3. Check the Device Status field for an error message. Look up the error code on Microsoft Support, if applicable, to fix the device.
4. Click "Troubleshoot" to open the Help and Support Center if no error code appears. Follow the onscreen prompts to pinpoint the root of the error and resolve the issue. Close Help and Support Center if the problem remains unresolved.
5. Click the "Resources" tab. Uncheck "Use Automatic Settings." Select "IRQ" if an error appears in the field below the conflicting device list.
6. Choose "Basic Configuration 0004" from the drop-down menu. If the error "Interrupt Request 04 Used By: <Device>" appears, double-click "IRQ" and change the value to 3. You must not have any devices connected to COM 2 or COM 4 for this to work.
7. Click "OK" to close each window. Exit from Device Manager. Click "OK" to close System Properties. If the COM 1 port still fails to respond, disconnect all peripheral devices from the computer except for the monitor, PS/2 mouse and keyboard.
8. Restart the computer. Connect the serial device to the PC after Windows XP has finished booting.