If you have installed Windows XP directly on your PC you will have tested the sound and found it works correctly. But, if you have installed it on top (even though you format it) of Windows 98 or 2000 you´ll see that the sound doesn´t work and isn´t detected. For this you need Realtek AC97 4.02 which installs the neccessary drivers easily and quickly so that the sound funcions in XP when it didn´t before, and it wasn´t even detected. They are universal drivers, so it doesn´t matter what type of sound card you have, as they work with the vast majority.