There are two different kinds of ports in use on your computer at any given time--physical ports and network ports. Sometimes, when your computer gives you an error message, you may wish to find out exactly which ports are in use and which resources are using them.
Discovering Which Input/Output Ports Are in Use
Click "Start" then "Control Panel." Navigate to "Device Manager." In XP you click the "System" icon then the "Hardware" tab.
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Select the "View" drop-down menu then select "Resources by type."
Click on "Input-Output Devices" to see a list of the ports in use.
Identifying Network Ports In Use
Open a command prompt by clicking "Start" and typing "cmd" in the "Run" box.
Type "cd /" to get to your C: drive.
Type "netstat -a" to see a list of all active port connections. If you wish to see more data or see the data displayed differently, typing "netstat a" will give you a menu of possible commands you can use and their results.