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  1. #1
    New Lounger
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    Extraneous COM ports (XP Pro) (5.1 /SP1)

    I have a Dell "legacy-free" Insprion 5100 without any built-in COM ports. In order to get COM ports I use a USB 2.0 hub and an RS-232 to USB adapter. Each time I plugged in the device, XP detected a "new" device and created a new COM port. After several iterations, I now have several COM ports defined that are not available for reassignment. For example, assigning a my PDA to a port shows several COM ports unavailable, even though I am certain that they are not in use. Is there a way to free up these unused ports? Is there a utility that works with XP to clean up these types of registry glitches?
    Thanks,
    Edward Heller

  2. #2
    Silver Lounger
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    Re: Extraneous COM ports (XP Pro) (5.1 /SP1)

    Press Windows and Pause/break keys on your keyboard simultaneously. The System Properties window will appear (if you don't have Windows key on your keyboard, click Start | Control Panel | Performance and Maintenance | System). Then click Hardware tab, and next Device Manager button. On Device Manager window, click little + sign in the square left of "Ports (COM and LPT)". Then right-click on each unwanted port and from pop-up menu choose Uninstall. To prevent creating of multiple COM port instances, keep your RS232 to USB adapter plugged in when you power on your computer.

  3. #3
    New Lounger
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    Re: Extraneous COM ports (XP Pro) (5.1 /SP1)

    Ah, there's the rub. These COM ports do not show up in the Device Manager, so I cannot uninstall them. I can see where they are defined in the registry, but I do not know how they are linked to other parts of the registry. That's why I was looking for guidance. Or can I simply prune the tree containing the key? I finally figured out that XP gets upset if the configuration of the hardware changes between shutdown and startup (and especially after a hibernate). So if I need to remove a device I do it before shutting down or after I start up.

  4. #4
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    Re: Extraneous COM ports (XP Pro) (5.1 /SP1)

    Hmm, I don't know so much about USB etc. since I don't use it for the moment. But after XP troubleshooting I've learned that not everything shows up in Device Manager, and in some cases when a driver install gets messed up you can end with several ghost monitors etc.

    You can try this:
    -in Device Manager click View | Show hidden devices, but I don't think they will show up.

    Better is to follow the workaround in:
    KB315539 Device Manager Does Not Display Devices That Are Not Connected to the Windows XP-Based Computer

    I quote:
    -at a command prompt type (and press Enter):
    set devmgr_show_nonpresent_devices=1
    -change dir. to WindowsSystem32
    -type and press Enter:
    -start devmgmt.msc
    -In Device Manager click Show hidden devices in View menu.

    You should be able to see installed devices that are not connected for the moment.

    I have a external serial port modem and this ... can not be found by XP if not present during boot, this odd behavior is "by design" as in Win2000. In Win95 you could turn off and on any time and just connect, ah well, so I agree with kaplinb; keep it connected on power up.

    Regards,
    Argus

  5. #5
    New Lounger
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    Re: Extraneous COM ports (XP Pro) (5.1 /SP1)

    Thank you. This was the essential solution. I was able to remove the devices using an appropriate mechanism. I wonder why this is not part of the Device Manager itself. If there is concern about simple users, perhaps it could be tied to admin privileges.
    Once again the Lounge comes through.
    Thanks.
    Edward.

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