Now you should be able to see all the device manager settings that are installed on your computer. If you see any yellow exclamation marks, it is likely that the hardware is installed, but the driver is not. You should right click and select the "properties" option at the bottom of the list to troubleshoot potential issues.
Install the driver from disc if you have it, or search for the driver on the manufacturer's web site. If you see any red markers, it means that the hardware cannot be found, or is no longer present in the computer. You have a few options here: make sure the hardware is securely installed in the system and try again, disable the hardware, or uninstall the driver for the hardware. One of these three options will likely make the "x" disappear.