A missing network adapter can be caused by several different issues, and solving the problem is typically fairly easy. One of the most common and easiest fixes for this problem is to update or install drivers for your network card; this is usually done during installation of the hardware or of an operating system (OS), but errors can occur. Sometimes the problem can be with the OS on the computer and something not being installed properly or becoming corrupted after an install. You can perform a repair installation that can often fix this problem, but you will likely need a full installation disk and not simply a recovery disk. A missing network adapter can potentially be a larger problem, however, and may require a full installation of your OS to fix the error.
One of the first steps you should take when dealing with a missing network adapter is to check in the properties or hardware device settings for the computer. How you access this information will depend on your OS, but it can often be found through the control panel, or by accessing the properties for your computer. Once looking at your hardware properties you should look for any devices with a mark or icon next to it to indicate a problem. If you cannot see your network controller at all, and your network adapter cannot be found even on this screen, you may need to try reinstalling the device or replacing it.
A missing network adapter is often caused by the lack of the proper drivers to allow your OS to properly recognize the network card or device. Many devices will come with a disc with drivers on it that you can install onto your computer to fix the error. If you do not have such a disc, then you may need to download drivers from the website of the manufacturer. Install these drivers and the network adapter will usually be found and work properly.
The problem causing the missing network adapter can also be an error with your OS and you may need to fix this issue before drivers can be properly recognized. If you have an installation disk for your OS, try running a repair install to replace any corrupted or missing files. This will solve many problems, though you may need to backup the data on your computer and completely erase your hard drive and install a fresh copy of your OS. If these steps do not find your network adapter, then it is possible the device itself is not working properly and you may need to replace it.