Changing Settings for an Installed Device
By default, Device Manager displays information about all currently installed and connected Plug and Play devices. To view devices that use non-Plug and Play drivers, as well as previously installed devices that are not currently connected, you need to tweak Device Manager slightly-for example:
- To view non-Plug and Play devices, open Device Manager and choose Show Hidden Devices from the View menu. In the default Devices By Type view, the formerly hidden devices appear under the Non-Plug And Play Drivers branch.
- To view devices that were once installed but are no longer attached to the computer, open a Command Prompt window using the Run As Administrator option and enter the command SET DEVMGR_SHOW_NONPRESENT_DEVICES=1. Then, from the same command prompt, type devmgmt.msc to open Device Manager. Choose View, Show Hidden Devices. The new instance of Device Manager now shows "ghosted" entries for devices that were once present. This technique is especially useful for fixing problems caused by leftover drivers after replacing a network card or video card-just delete the ghosted device.
- To see advanced details about a device, open the properties dialog box for the device and look on the Details tab. The value shown under Device Instance Id is especially useful for tracking down devices that are detected incorrectly. The full details for a device ID shown here can be found in the registry, under HKLM\System\Current- ControlSet\Enum. Although we don't recommend idly deleting the found key, this information might provide enough information to figure out why a device isn't being identified properly.
Setting the DEVMGR environment variable as described in this section affects only the instance of Device Manager launched from that Command Prompt window. If you want the change to be persistent, open Control Panel, open System, click Advanced System Settings, click Environment Variables on the Advanced tab, and define a new variable for this setting. If you add the variable to the User Variables section, the setting applies only to the current user; if you edit the System Variables section, the extra information is visible in Device Manager for all users of the current computer.
Adjusting Advanced Settings
Some devices include specialized tabs in the properties dialog box available from Device Manager. Controls on these additional tabs allow you to change advanced settings and properties for devices-for instance:
- Network cards and modems typically include a Power Management tab that allows you to control whether the device can force the computer to wake up from Sleep mode. This option is useful if you have fax capabilities enabled for a modem, or if you use the Remote Desktop feature over the internet on a machine that isn't always running at full power. On both portable and desktop computers, you can also use this option to allow Windows to turn off a device to save power.
- The Volumes tab for a disk drive contains no information when you first display the properties dialog box for that device. Click the Populate button to read the volume information for the selected disk. You can then choose any of the listed volumes and click the Properties button to check the disk for errors, run the Defrag utility, or perform other maintenance tasks. Although you can perform these same tasks by right-clicking a drive icon in the Computer window, this option might be useful in situations where you have multiple hard disks installed and you suspect that one of those disks is having mechanical problems. Using this option allows you to quickly see which physical disk a given volume is stored on.
- DVD drives offer an option to change the DVD region, which controls what discs can be played on that drive.
The DVD Region setting actually increments a counter on the physical drive itself, and that counter can be changed only a limited number of times. Be extremely careful with this setting, or you might end up losing the capability to play any regionally encoded DVDs in your collection.
- When working with network cards, you can often choose from a plethora of settings on an Advanced tab, as shown in the following example. Randomly tinkering with these settings is almost always counterproductive; however, you might be able to solve specific performance or connectivity problems by adjusting settings as directed by the device manufacturer or a Microsoft Knowledge Base article.
- Self-powered USB hubs (hubs that are connected to an AC power source) include a Power tab. Use the information on the Power tab to calculate the amount of power required by devices that draw power from the hub. If the total power requirement is more than the hub can supply, you might need a new hub.
Viewing and Changing Resource Assignments
If you're a PC veteran, you probably remember struggling with MS-DOS and early versions of Windows to resolve device conflicts, most often when two or more pieces of hardware lay claim to the same IRQ. On modern computers with an Advanced Configuration and Power Interface (ACPI) BIOS, those sorts of conflicts are practically extinct. In the original design of the IBM Personal Computer, IRQs were in short supply, with a total of 15 available, and many of those were reserved by system devices, such as communications ports, keyboards, and disk controllers. With older Windows versions, problems could occur when adding a new device such as a sound card or network adapter. If the new device was hardwired to a specific IRQ that was already in use, or if there were no free IRQs, the device simply would not work.
On computers running Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, or Windows 7 with a mix of PCI add-in cards, the operating system takes advantage of the ACPI features on the motherboard to share scarce IRQs among multiple devices. In Device Manager, you can check resource allocations at a glance by choosing Resources By Type or Resources By Connection from the View menu.
Under most circumstances, you cannot use Device Manager to change resource settings for a specific PCI or USB device. Resources are allocated automatically by the operating system at startup, and the controls to change resource settings are unavailable. Resource conflicts are most common with legacy devices that are not fully compatible with Plug and Play. In the rare event that you experience a resource conflict, you might be able to adjust resource settings manually from the Resources tab: clear the Use Automatic Settings check box, and cycle through different settings to see if any of the alternate configurations resolve the conflict.
If you suspect that a hardware problem is caused by a resource conflict, you can access an overview of resource usage by opening the System Information utility (Msinfo32.exe), which is found on the All Programs menu under Accessories, System Tools. Open Hardware Resources in the console pane, and pay special attention to the Conflicts/Sharing entry and the Forced Hardware item. Don't be alarmed if you see a number of devices sharing a single IRQ; that's perfectly normal.
For legacy devices whose resources can't be assigned by Windows, you'll need to adjust jumpers on the card or device, or use a software-based setup/configuration utility to change resource settings for that device.
Resource conflicts prevent a device from working
If two devices are in conflict for a system resource, try any of these strategies to resolve the problem:
- With PCI and PCI Express devices, try swapping cards, two at a time, between slots. On some motherboards, IRQs and other resources are assigned on a per-slot basis, and moving a card can free up the proper resources. Check the motherboard documentation to see which IRQs are assigned to each slot, and experiment until you find an arrangement that works.
- If the conflict is caused by a legacy (ISA) device, replace it with a Plug and Play- compatible PCI device.
- Use jumpers or a software utility to change settings on a legacy device so that it reserves a different set of resources. You will need documentation from the manufacturer to accomplish this goal.
If you have problems with PCI devices, the device itself might not be to blame. When drivers and ACPI BIOS code interact improperly, conflicts can result. Check for an updated hardware driver (especially if the current driver is unsigned), and look for a motherboard BIOS update as well.