Windows

'Ghost' Devices in Device Manager

'Ghost' devices can be caused to remain in Device Manager when devices such as netcards or CD-ROM / DVD drives are replaced without uninstalling the original device first.  Before permanently removing any hardware, for example when upgrading, you should always:

  1. Go into Control Panel, Add/Remove Programs and uninstall any software or drivers listed there that are associated with a device to be removed.
  2. If the device is still present in Device Manager after uninstalling any drivers, right-click it and choose Uninstall.

Though undesirable, ghost devices are often not a particular problem, and most users remain unaware of them because normally they aren't visible in Device Manager.  However, while other types of ghost device such as netcards can also cause problems, ghost CD-ROM / DVD drives seem to be more frequently a problem than any other type of device, probably more than all the other types of device added together.

A typical scenario is that someone upgrades a CD-ROM drive to a burner, or a CD-burner to a DVD-burner, by just physically removing the old drive and reconnecting the new one in its place.  Then when the machine boots up, either the new drive is not detected, or it has a yellow exclamation mark in Device Manager signifying it has a problem, or everything appears normal in Device Manager, but the burning software doesn't interact with it in the expected manner.

The cure for all types of device is to remove all the old ghost devices and the new device and then reboot to let the new device be redetected properly.  Unless there is also some other problem such as a shortage of system resources like DMA or IRQs, this procedure will normally work.

Important:

  1. In the following procedures the hidden devices made visible will include legitimate devices such as USB printers or Firewire cameras that happen not to be connected to the PC at the moment.  Naturally, these should be left alone.
  2. The hidden devices may include an 'Unknown Device' with a yellow question mark or exclamation mark.  These often used to occur on laptops such as ThinkPads in W98, but I've also seen them on desktops in W2k as well.  They're difficult!  They may be a genuine problem device, which, if I advise you to remove, would solve your problem, but they may also be a genuine device associated with the motherboard which if uninstalled would uninstall the entire hardware tree, necessitating multiple reboots and rummaging in drawers for driver installation CDs as all the hardware is redetected again!  I can give no advice here.  I can only explain the problem and leave you cursing, as I do, the stupidity of allowing a system critical device to go under the catchall handle 'Unknown Device'!

    Of course, if you are confident that you have all your driver CDs and are not short of time, then cleaning out the hardware tree can sometimes be a good thing.

    But there again, if it ain't broke, why fix it?

In W2k:

  1. Sign on as an Administrator
  2. Right-click My Computer and choose Properties, Advanced, Environment Variables.  In the top half of the dialog box, the User variables for Administrator, choose New, enter devmgr_show_nonpresent_devices as the Variable Name, and 1 as the Variable Value.  Click Ok three times.  This is a permanent change, delete the new variable once the job is done if you wish to revert to the simpler Device Manager display.
  3. Go into Device Manager.
  4. Choose Show devices by connection.
  5. Choose Show hidden devices.  Ghost devices will normally now be visible and obvious as not being attached to anything in the main hardware tree.
  6. Uninstall any devices, in our example such as old CD-ROM / DVD drives, that you know have been permanently removed, and any new ones that you are currently trying to install.
  7. Reboot.  The new hardware should now be redetected properly.

In W9x (here my memory is a little hazy as I haven't worked with W9x for a while):

  1. Reboot into Safe Mode.
  2. Go into Device Manager.
  3. Choose Show devices by connection.
  4. Choose Show hidden devices.  Ghost devices will normally now be visible and obvious as not being attached to anything in the main hardware tree.
  5. Uninstall any devices, in our example such as old CD-ROM / DVD drives, that you know have been permanently removed, and any new ones that you are currently trying to install.
  6. Reboot.  The new hardware should now be redetected properly.