Windows XP Hacks [Electronic resources] نسخه متنی

Hack 96 Uncover Hidden Hardware with the Device Manager

Hardware ghosts and other hidden devices can
cause system conflicts, and the Device Manager won't
report on them. This hack forces the Device Manager to uncover all
your hidden hardware so you can resolve any conflicts.

One of the strangest hardware
problems you'll encounter in XP are hidden and
ghosted hardware devices that are invisible to
you but that may cause system conflicts. You won't
be able to see them in the Device Manager [Hack #95]. When you use that troubleshooting
tool, you won't be able to uncover any problems they
may be causing.

There are several types of these hidden and
residential gateways:optimizingghosted devices that are hidden by the
Device Manager. Non-plug-and-play printers, drivers, and similar
devices don't show up. Most newer devices are
plug-and-play, so you'll most likely encounter this
problem only if you have old hardware attached to your PC.
(Plug-and-play devices are automatically recognized and installed in
XP.) In this instance, the device is physically present on your PC,
but the Device Manager doesn't show you that
it's there.

Then there are the so-called
nonpresent or
ghosted devicesdevices that
you've removed from your system without doing an
uninstall, or whose uninstallation did not work properly. These
devices aren't physically present in your system,
but XP treats them as if they were and devotes system resources to
them. For example, if you physically remove an old network card
without doing an uninstall, it may cause IP and other kinds of
conflicts, because XP treats it as if it were still in your system.

The Device Manager also may not give you details about
USB devices that you only temporarily
use and that you frequently attach and removefor example, MP3
players that you attach to your PC only when you want to add or
delete MP3 files from them. Even when these devices
aren't present in your system, XP devotes resources
to them. If you replace one USB device with another of the same
model, it's best to go through the uninstall process
rather than just swap them.

And then there are devices that you may have moved from one slot to
another. XP may believe that they are actually present in two slots,
so it devotes resources for both slots to them.

Displaying these hidden devices can help with troubleshooting. For
example, a hidden device could possibly conflict with a nonhidden
device. And there may be instances in which you will want to
uninstall hidden devicesfor example, when
you've moved a non-plug-and-play network card from
one slot to another and want to uninstall it from one slot.

But to do this kind of troubleshooting you'll need
to force the Device Manager to display information about the devices;
otherwise, you won't know how to solve the problem.

Forcing the Device Manager to
display non-plug-and-play
printers, drivers, and similar devices is a simple matter. Run the
Device Manager by typing devmgmt.msc at a command
prompt and pressing Enter, and then choosing View Display
Hidden Devices, and they will appear.

Displaying ghosted or nonpresent devices takes a
little more work. You'll set a system-wide
environment variable that forces the Device Manager to display them.
First, right-click on My Computer and choose Properties
Advanced Environment Variables.
The Environment Variable dialog box
opens. This dialog box let you set system variables for the entire
system or for individual users. Environment variables control a
variety of XP features, such as the location of your
Windows directory and TEMP
directories and the filename and location of the command processor
that will launch when you run the command prompt.

There are two sections in the Environment Variables dialog box:
"User variables" and
"System variables." To apply the
variable to a single user, use the "User
variables" dialog box; to apply the variable to all
users, use the "System variables"
dialog box. In this case, you'll want to create the
variable system-wide, so click New in the "System
variables" section. The New System Variable dialog
box appears. For "Variable name,"
type devmgr_show_nonpresent_devices. Once
you've created the name, you need to give it a
value. To turn the setting on, type 1 in the
"Variable value" box. You can see
the box filled out properly in Figure 12-3. Click OK
and then OK again.

Figure 12-3. Setting the Device Manager to always show ghosted devices

So, now you've set the system variable properly, but
the Device Manager won't display ghosted devices
yet. You first have to tell it to display them. Run the Device
Manager by typing devmgmt.msc at a command prompt
or the Run box and pressing Enter. Then, choose View
Display Hidden Devices and the ghosted devices will appear, as shown
in Figure 12-4. You should see quite a few devices
now, including a lengthy list of non-plug-and-play drivers.
Typically, devices that are not currently present on your PC will be
shown as gray, rather than the black that connotes present devices.
You may also see some devices listed more than once, as shown in
Figure 12-4.

Figure 12-4. Displaying ghosted devices in the Device Manager

Now, use the Device Manager to troubleshoot any of those ghosted
devices, as detailed in [Hack #95]. If you find any ghosted devices that
you will no longer use on your PC, uninstall them from the Device
Manager by right-clicking on the device and choosing Uninstall.

12.3.1 Hacking the Hack

If you want to use the Device
Manger only on occasion to show ghosted devices and
don't want to add another environment variable to
your system, you can add the variable on an instance-by-instance
basisfor example, for a single time that you run the Device
Manager. At the command prompt, type set
devmgr_show_nonpresent_devices=1 and press Enter. You
won't get a prompt in response; the command prompt
will stay blank. At the same instance of the command prompt, type
start devmgmt.msc and press
Enter. The Device Manager will launch in a separate window. Now,
enable the Device Manager to show ghosted devices in the same way you
did previously in this hack.

Keep in mind that you have to run the Device Manager from the same
instance of the command prompt in which you typed
devmgr_show_nonpresent_devices=1. If you run the
Device Manager outside the command prompt, it won't
display ghosted devices.