Thursday, September 13, 2012

Modifying devices and drivers on windows

In this post I am going to show how to reset the auto numbering of new devices, how to see drivers for devices that are not connected on your pc and how to see which usb is connected to which usb controller in order to maximize the data throughput by using both controllers (which is the case of most modern laptops).

If you have installed a software driver for a virtual device (like if you install openVPN you get the TAP-Win32 Adapter V9 device) you may have noticed that the numbering of those devices increments no matter if you have deleted some previous devices.  If you have just deleted the last device you added and you want the new device to get the same numbering, you may reset the counter by modifying the list of numbers in:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Network\{big long hex number}\Descriptions

There you will see the devices as a REG_MULTI_SZ key which contains the given numbers in the Data field. For example I have
Virtual Machine Network Services Driver with value 1 2 3 (each element on a separate line). This means that if I install another Virtual Machine Network Services Driver it will be named Virtual Machine Network Services Driver 4. You can modify this list and you are ready to give the same number over and over again (if you delete the previous device first).

Moreover, sometimes it’s useful to see the installed drivers for devices that are not connected to your pc anymore. Device manager will show them if you have set the environment variable devmgr_show_nonpresent_devices to value 1. You can either set it in your environment variables (right click on my computer, properties, advanced properties, environment variables) or you can start a command line and post the following commands:
set devmgr_show_nonpresent_devices=1
cd %SystemRoot%\System32
start devmgmt.msc
A final tip I want to give in this post is how to see which usb port is connected on which usb controller (to maximize the transfer rate). You can see that if you click on the device manager the View-->Devices by connection option in the menu.

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