I am running on Windows 8.1 64-bit OEM, and have installed Windows Updates and drivers for my system (the system was built just over a month ago).

This included drivers for a USB cellular modem (made by uBlox), and I mapped the virtual COM ports it enumerates to known locations using Device Manager (it happens to enumerate around 6 COM ports, I wanted these to number from COM11 through COM16).

I can see the location for this information in the registry at: HKLM\SYSTEM\CurrentControlSet\Enum\USB\VID_xxxx&PID_xxxx\...

Normally I run with the USB cellular modem powered off (and have left it in this state for a few days). Hence the USB cellular modem is only visible when showing "hidden devices" in Device Manager.

This week I left my system alone for a few hours and after rebooting and powering the USB cellular modem I noticed that the virtual COM port mapping I defined was lost.

I repeated this (by cloning a previous image of the harddrive and repeating) and it seems that Windows automatically removes the USB cellular modem from the system (i.e. it no longer appears as a device in Device Manager and all of the registry keys in HKLM\SYSTEM\CurrentControlSet\Enum\USB\... have been removed).

To be clear, this system has *only* Windows 8.1, Window Updates and drivers on it (no other 3rd party software, and no registry cleaners).

Does Windows 8.1 contain a mechanism to "clean-out" old USB devices (such as USB cellular modems) that it hasn't seen on the system for a period of time (as part of some house-keeping)?

Is there any mechanism in Windows 8.1 that can explain this behaviour?

Thanks

• Moved by Franklin ChenMicrosoft contingent staff Monday, June 15, 2015 6:33 AM Win8.1 IT pro

I am running on Windows 8.1 64-bit OEM, and have installed Windows Updates and drivers for my system (the system was built just over a month ago).

This included drivers for a USB cellular modem (made by uBlox), and I mapped the virtual COM ports it enumerates to known locations using Device Manager (it happens to enumerate around 6 COM ports, I wanted these to number from COM11 through COM16).

I can see the location for this information in the registry at: HKLM\SYSTEM\CurrentControlSet\Enum\USB\VID_xxxx&PID_xxxx\...

Normally I run with the USB cellular modem powered off (and have left it in this state for a few days). Hence the USB cellular modem is only visible when showing "hidden devices" in Device Manager.

This week I left my system alone for a few hours and after rebooting and powering the USB cellular modem I noticed that the virtual COM port mapping I defined was lost.

I repeated this (by cloning a previous image of the harddrive and repeating) and it seems that Windows automatically removes the USB cellular modem from the system (i.e. it no longer appears as a device in Device Manager and all of the registry keys in HKLM\SYSTEM\CurrentControlSet\Enum\USB\... have been removed).

To be clear, this system has *only* Windows 8.1, Window Updates and drivers on it (no other 3rd party software, and no registry cleaners).

Does Windows 8.1 contain a mechanism to "clean-out" old USB devices (such as USB cellular modems) that it hasn't seen on the system for a period of time (as part of some house-keeping)?

Is there any mechanism in Windows 8.1 that can explain this behaviour?

Thanks

• Merged by Deason WuMicrosoft contingent staff, Moderator Wednesday, June 17, 2015 7:19 AM Duplicate

There is another entity that manages COM port names, separate from the thing that manages the Enum tree.  Maybe it could reclaim stale COM name assignments. The WDK (drivers)  forum is the best place to ask about this.

Regards,

-- pa

• Edited by Pavel A Wednesday, June 17, 2015 7:02 AM

There is another entity that manages COM port names, separate from the thing that manages the Enum tree.  Maybe it could reclaim stale COM name assignments. The WDK (drivers)  forum is the best place to ask about this.

Regards,

-- pa

• Edited by Pavel A 12 minutes ago

Hi

I checked the schedule task, this task intend to remove older versions of drivers that are no longer needed. The most current version of each driver package will be kept. This task will also remove state used by devices that have not been detected on this system for a long period of time.

This task could be disabled/configured by using administrator permission. You could disable this task and give it another try. And unfortunately its actions cannot be edit.

How ever since this task run as system account by default (could be changed), try edit the registry entry permission settings see if it works.

Regards,

D. Wu

Hi,

Since this tasks action is custom handler, so I am afraid that we cannot browse/edit the script used by this task. For USB Device Registry Entries, since Registry settings for configuring USB driver stack behavior are also included in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB class, I think this schedule task is not so thoughtful for every entry in that class. If you need keep this task running, try another solution as mentioned in my last reply. Prevent the registry value from getting deleted by system account. But I am afraid that there will be many error entries in event log.

Regards

D. Wu