If your computer’s Device Manager is displaying an “unknown PCI device” in its list of installed hardware components, it’s usually caused when Windows cannot recognize the video display or the chipset.
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PCI Device Drivers Download
This can happen if the device’s drivers become corrupt or have been deleted. Solving this problem involves reinstalling the chipset or graphics display drivers to see if that works. Use a little detective work to further narrow down your choices. For example, if you see an “unknown PCI device” listed in PCI Driver Device Manager, check the category for Display Adapters and see if anything is listed there. If not, the unknown device could be your graphics adapter.
PCI Device Driver Installation CD
Did you save all of the PCI device driver installation CDs that came with your computer and various hardware components you’ve added over the years? If so, you can try reinstalling the PCI device driver for the suspected unrecognized components. But that’s a shot in the dark. Before you start installing PCI device drivers one by one in an attempt to fix the mysterious damaged one, consider doing a little investigative work.
Updating PCI Device Drivers and Windows Registry
This task involves looking at the Windows registry which is extremely risky. Anytime you even look at the registry, make sure to make a backup first just to be safe. Once you’ve backed up the registry, you can take a look inside to see the information stored about each PCI (Peripheral Component Interconnect) device. Information including Vendor ID, Device ID, Subsystem ID, and Hardware Revision ID is stored in:
HKEY_LOCAL_MACHINE\CurrentControlSet\ Enum\PCI\VEN_<vendorID>&DEV_<deviceID>&SUBSYS_ <subsystemID>&REV_<hardwarerevisionID>
PCI Device-Specific Instructions
Each of the words in brackets features a number. For example, <vendorID> is replaced by the hexadecimal number assigned for that particular vendor. By browsing the registry for PCI device driver info in search of an entry that has a class of “unknown” you can then look at the primary key above it and identify the vendor.
First, go into the Registry Editor by going to the Start Button, clicking Run, and typing Regedit. Make a backup if you haven’t already. At the very least, create a System Restore point using System Restore if you have Windows XP or Vista. Now, find the HKEY_LOCAL_MACHINE\CurrentControlSet\Enum\PCI VEN key (depending on your operating system the “CurrentControlSet” may be missing, in which case go directly to HKEY_LOCAL_MACHINE\Enum\PCI\VEN key).
Expand one of the keys to see the subkeys below. Click the subkey and you should see a list of information such as Class, DeviceDescription, and Mfg. This data tells you what type of device it is (such as a display adapter), a description, and the manufacturer.
Please keep following the PCI Device Registry Edit steps!
Continue looking at each PCI device driver-related entry until you find one that lists “unknown” in the class field. Now, you’ve found the unknown PCI device. Click the key directly above it and write down that value because it contains the vendor codes including the Vendor ID, Device ID, Subsystem ID, and Hardware Revision ID. Exit the registry editor.
Now you have a bunch of numbers that make absolutely no sense without further help. Fortunately, there’s a vast database of PCI device driver information that you can use to identify your PCI device. Once you know which device you have, then you can go in search of the required PCI device drivers.
PCI Device Driver is almost there
Click the Vendors by ID link and search for the vendor ID that you just discovered. Each vendor ID number will have an “0x” in front of it. For example, if you’ve discovered a vendor ID of 10B7, scroll down to 0x10B7 and you’ll find out that the vendor is 3Com Corporation. Click the vendor’s link and then scroll through until you find your Device ID. For example, if your device ID was 9004, you’ll look for 0x9004 and find out that the mysterious PCI device is a 3Com Ethernet XL TPO 10Mb Ethernet NIC (3C900 TPO) network adapter.
Ensuring You have the right PCI Driver
Now that you have this information, you can go to the vendor’s website in search of the appropriate PCI device driver.
Your computer may not recognize a PCI device but the information is there if you’re willing to dig for it. Anytime you enter the Windows registry, use great care.