The codecs will be loaded when you install the latest video drivers, provided by the manufacturer of the computer, the motherboard manufacturer, or the video card manufacturer.
Delete the old drivers before installing new ones.
Codecs will be loaded by installing players, such as Adobe flash player. Codecs will be loaded by installing player software, such as Div X, Cyberlink, etc...
But older computers with single core processors, may not be capable, or may not have the drivers which include the newest codecs. In other words, you may be obsolete.
Up grading an older computer with a new video card usually does not produce the result that you are looking for. It may be time to consider a newer computer. Think quad core.