XP SP2 missing com ports

G

Gman

This seems to be a common problem that has been posted on various boards.

In device manager, all of my com ports except for com1 have disappeared.
This prevents me from using the built in modem on my notebook. When I
attempt to activate the modem, windows displays a message that the port
cannot be opened evn though the port does not show as active. Microsoft has
a tool called COMDisable which is supposed to display the avaialable com
ports and lets you activate or deactivate the ports without having to
manually editing the registry. This tool is supposed to run on XP, but it
does not run on my system and from reading numerous posts others have the
same issue. The tool will start and then immediately shut down.

A search of MS knowlege base does not turn up any solutions to the missing
com port issue other than to run COMDisable and there is no solution posted
as to why it will not run on certain machines.

If anyone has answers they will be greatly appreciated.
 
S

smlunatick

This seems to be a common problem that has been posted on various boards.

In device manager, all of my com ports except for com1 have disappeared.
This prevents me from using the built in modem on my notebook. When I
attempt to activate the modem, windows displays a message that the port
cannot be opened evn though the port does not show as active. Microsoft has
a tool called COMDisable which is supposed to display the avaialable com
ports and lets you activate or deactivate the ports without having to
manually editing the registry. This tool is supposed to run on XP, but it
does not run on my system and from reading numerous posts others have the
same issue. The tool will start and then immediately shut down.

A search of MS knowlege base does not turn up any solutions to the missing
com port issue other than to run COMDisable and there is no solution posted
as to why it will not run on certain machines.

If anyone has answers they will be greatly appreciated.

The COM port setting for most internal (built-in) do not get listed
under the Ports section. These built-in internal modems are listed
under the Modems section. You may have to re-install the correct
drivers.
 
G

Gman

The port that the modem used to use was previously listed in device manager
in the Ports section. When the listing disappeared the modem stopped
working.

I have reinstalled the modem driver several times to no avail.

When I try to activate or query the modem Windows reports that the port
cannot be opened. My understanding of how XP handles port assignments is
that even after a device is removed/uninstalled the original port assignment
is kept track of by XP and XP will then assign the next available port when
a new device is added.

The previously mentioned COMDisable tool is supposed to allow seeing the
active ports and deactivate them, or to activate an unassigned port. This
would probably solve my problem except that the tool will not run. It
starts then immediately shuts down. This behavious seems to be common and I
haven't been able to find an answer as to why.

My alternative is to find the section in the registry that the tool eidts
and do some manual editing -- the problem is I have no idea where to start
looking in the registry.
 
R

R. McCarty

XP doesn't show Phantom/Unpowered-Connected Plug-&-Play devices
even with "Show Hidden Files" enabled. To view 100% of the devices in
Device Manager you have to add a System Environment Variable:
DevMgr_Show_NonPresent_Devices
and set it's value = 1. Once applied, you can see all your non-active ports.
 
G

Gman

Thank you for the tip.
I assume this is inserted in the registry? If so, can you tell me where it
should go? If not in the registry, how do I apply the variable?

Thanks
 
R

R. McCarty

System Properties, Advanced (TAB), Environment Variables, System
[ Bottom Section ], New
 

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