XP: Howto reassign COM port numbers, and identify COM devices that are present

Posted on 2006-04-01
Last Modified: 2009-01-23

I have installed a new two port serial card into a custom (mobo = intel D845GRG, a USB card, a NIC, and the new serial card) WindowsXP computer.  The new device was discovered by the operating system, and it did prompt for drivers for the card (NetMos).  However, the COM port numbers that are assigned are COM13 and COM14, but the application which needs to print to these devices can only access devices up to COM8.  

Using the device manager to look at the COM devices, it shows that COM1 through COM12 as being (used).  The mobo has one onboard serial port, and there are no other serial ports in the computer.  Sandra has been installed, and it only sees COM1.

I have manually reassigned the COM port numbers to be 3 and 4, but I'm concerned that I may be conflicting with something that I don't know about.  

Note that other serial cards have been installed into this computer, and the application (CAD, used to create and print to different large format printers and cutters) did not print through those cards.  Those cards were subsequently removed.  I'm suspecting that there are some phantom space holders that are incrementally bumping the COM port number as part of each install.  

1) How can I determine what COM port devices are actually present and which ones are phantoms.
2) Is there a way to "reset" or otherwise "prune" the list of phantom COM devices.
3) How to test the basic life of a COM port, and positively identify whether I'm plugged into COM # or 4, without sending a test-print to the device (which is subject to possible application failure).
Question by:ChrisEddy
    LVL 3

    Accepted Solution

    If you have default COM ports of 13 and 14 with your new card, and Device Manager shows 1-12 in use, then you need to do some cleanup.
    In Device Manger, remove all of the COM ports and reboot. That should fix this. If your are nervous about this, then remove only COM ports 3-12 and reboot as instructed.
    If that does not work, do the same thing but do it in SafeMode, which allows you to see and remove duplicate phantom drivers; COM port and otherwise.
    I would not be surprised to see "same number" multiple COM ports in your case(phantoms). All must be removed.
    LVL 11

    Expert Comment

    by:Joseph O'Loughlin
    Another wrinkle to the above is to try hardware profiles.
    What is the application as all com ports are not created equally.

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