How much do you know about ghost devices? Solve this month's Windows IT Pro Update Reader Challenge, and you might win a prize!

Take the August 2009 Reader Challenge:
Could your computer be haunted? I received several queries from readers with the same problem: Ghost devices on computers. Several readers wrote that when trying to install a second NIC, the set up failed because Windows kept insisting that the IP Address was already in use by another NIC.

The settings for the first NIC in the computer didn't use the IP Address in question. Other readers wrote that USB devices that were frequently removed (and attached again the next time they were needed) occasionally failed with errors about "already in use." One reader wrote that the Processes tab of Task Manager was showing processes required for devices that weren't attached to the computer.

Of course, I responded with the obvious advice: "In Device Manager, click the View command, and select Show Hidden Devices." Every reader wrote back with one of the following responses: "I already tried that"; or "Your suggestion didn't work."

OK, the only reasonable answer (and I use the word "reasonable" sarcastically because I don't believe in ghosts) is that these computers are haunted, and the ghost devices can't be found.

Is that right? Your Challenge this month is to answer these questions:

Question #1: What is the default definition of Hidden Devices in Device Manager?
A. Devices with corrupt drivers or devices that have no drivers
B. Devices that are not Plug and Play

Question #2: Is there a way to see non-existent devices in Device Manager?
A. No
B. Yes

How to Play:
Email your solution (don't use an attachment) to challenge@windowsitpro.com by August 25, 2009. You MUST include your full name, street mailing address (no P.O. Boxes), and a telephone number. Without that information, we can't send you a prize if you win, so your answer is eliminated, even if it’s correct.

I choose winners at random from the pool of correct entries. I’m a sucker for humor and originality, and a cleverly written correct answer gets an extra chance. Because I receive so many entries each month, I can't reply to respondents, and I never respond to a request for an email receipt.

Look for the solutions to this month's problem here at the August 2009 Reader Challenge. My editor won't have the answers up on the site until Sept. 22, when the September Reader Challenge goes out via the Windows IT PRO Update Newsletter (she's a bit slow).

July 2009 Reader Challenge Winner:
Congratulations to Mark Ellender of Texas, the winner of our July 2009 Reader Challenge. He wins a copy of Head First Networking from O'Reilly Media.

Related Reading:

Answers to the August Challenge
Question #1: B
Question #2: B

In order to see non-existent devices when you select View Hidden Devices you have to change the way Device Manager defines a hidden device. When you remove a device without uninstalling it (such as replacing a NIC), Device Manager remembers the original device and its settings, even though it doesn't list the device (even in Hidden Devices). There are several ways to force Device Manager to report all the devices it's tracking, but I prefer to use one of the following methods.

For a permanent configuration change, change the registry as follows:
1. Open the registry editor and go to: \[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session ManagerEnvironment\].
2. Create a New Key of the type REG_SZ (String Value) named DEVMGR_SHOW_NONPRESENT_DEVICES.
3. Enter the value 1.

You may have to restart Windows to have the new setting take effect. Then open Device Manager and select View, Hidden Devices. When you find the ghost, right-click its listing and choose Uninstall.

For a one-time configuration change (to avoid having any other user see ghost devices), open a command window and perform the following tasks:
1. Type set devmgr_show_nonpresent_devices=1 and press Enter. (You won't see any response.)
2. Then, in the same command window, type startdevmgmt.msc and press Enter to open Device Manager.
3. Choose View Hidden Devices to show the ghost devices.
When you find the ghost, right-click its listing and choose Uninstall. (When you close Device Manager, the configuration reverts back to the default definition of Hidden Device.

Two things to remember:
1. A ghost device could be the result of a USB device that you attach to different USB ports. Windows remembers the USB port in use (and assigns resources to support it, even after you remove the device). When you attach the same device to a different USB port, Windows thinks it's a second device. The same paradigm exists for PC cards you insert in your laptop.
2. When you want to remove a device from a computer (such as a NIC), open Device Manager and uninstall the device. This prevents the device from haunting the computer.