Each error code shown for a device includes a description as well as a suggested action you should take to try to resolve them. Table 13-1 summarizes the common error codes you'll see and describes the suggested actions you should take to resolve them. Most of the actions assume you have the device's Properties dialog box open to the General tab.

If the suggested action doesn't resolve the problem, you might be able to use the Hardware Troubleshooter to resolve the problem. Double-click the device in Device Manager, then click Troubleshoot in the General tab. Keep in mind that if the device drivers aren't installed properly, you won't have a Troubleshoot option. Instead, you'll have a Reinstall Driver button. Clicking Reinstall Driver starts the Hardware Update Wizard discussed in the section entitled "Updating a Device Driver" earlier in this chapter.

Anyone who remembers IRQ conflicts will be thankful that current computers support ACPI BIOS. With ACPI BIOS, resources are allocated automatically by the operating system at startup, and multiple devices can share the same IRQ settings. These changes mean IRQ conflicts are largely a thing of the past. However, ACPI depends on Plug and Play, and devices that are not fully compatible can sometimes cause problems, particularly ISA devices.

Troubleshooting: Check the device slot configuration

Some conflicts occur because PCI interrupts are sharable, while ISA interrupts are nonsharable. Typically, this is a BIOS problem. If a device is in a PCI slot but the slot is configured in BIOS as "reserved for ISA," a conflict can occur. You must change the BIOS settings rather than the resource configuration to resolve the problem.

If you suspect a device conflict is causing a problem with the current device, check the Conflicting Device list in the lower portion of the Resources tab. It will either list No Conflicts or the specific source of a known conflict. In Device Manager, you can quickly check resource allocations by choosing Resources By Type or Resources By Connection on the View menu.

In Figure 13-9, both ISA and PCI devices are using IRQ settings. You'll note each ISA device has a separate IRQ setting, while multiple PCI devices share the same IRQ settings. This is very typical. Note also that the PCI Modem device has a question mark as an icon. This is because the device isn't configured properly, not because there's a conflict. In this example, there are no conflicts.

Figure 13-9. View resources by type or resources by connection to check resource settings in Device Manager

Another way to check for conflicts is to use the System Information utility (Msinfo32.exe). Start the System Information utility by clicking Programs or All Programs, Accessories, System Tools, and then System Information. In System Information, expand Hardware Resources, and then select Conflicts/Sharing.

As shown in Figure 13-10, a list of all resources that are in use is displayed. Again, keep in mind that devices can share IRQ settings thanks to ACPI, so what you are looking for are two unrelated devices sharing the same memory addresses or I/O ports, which would cause a conflict. Keep in mind related devices can share memory addresses and I/O ports. In the example, the Standard VGA Graphics Adapter and the Intel 82845 Processor to AGP Controller share the same memory addresses and I/O ports. That's okay because they are related. The PCI Bus is using a memory address space with these devices as well, which is as it should be because Standard VGA Graphics Adapter and the Intel 82845 Processor to AGP Controller are both PCI devices.

Figure 13-10. Use System Information to check for resource conflicts

You can try to resolve resource conflicts in several different ways. Some devices use jumpers to manage resource settings, and in this case, the operating system cannot control the resource settings. To make changes, you must shut down the computer, remove the device, change the jumper settings, and then replace the device. In some cases, the jumpers are managed through software rather than an actual jumper switch. Here, you would use the device setup or configuration utility to change the resource settings.

For PCI devices, you can try swapping the cards between PCI slots. This will help if the IRQ or other resource settings are assigned on a per-slot basis, as is the case with some motherboards. You might be able to check the motherboard documentation to see which IRQ interrupts are assigned to which slots. In any case, you'll need to experiment to see which card configuration works.

For PCI devices, a conflict could also be caused by the device driver and the way it works with the ACPI BIOS. You should check to see whether an updated device driver and a BIOS update are available. Installing one or both should resolve the conflict.

As a last resort, you can change the resource settings manually for some devices in Device Manager. In the Resources tab, shown in Figure 13-11, select the resource type that you want to work with. If you can make a change, you should be able to clear the Use Automatic Settings option and then see whether any of the alternate configurations in the Setting Based On box resolve the conflict. Keep in mind that you are now manually managing the resource settings. To allow the Windows operating system once again to manage the settings automatically, you must select Use Automatic Settings.

Figure 13-11. For legacy devices, you can use a different configuration to see whether this resolves a conflict