Please write down with paper and pencil, the items listed in Device Manager, under Sound, video and game controlles
For instance, this machine that I'm typing from has:
Auodio Codecs
Legacy Audio Drivers
Legacy Video Capture Devices
Media Control Devices
Realtek High Definition Audio
Video Codecs
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Have you checked in BIOS/CMOS setup to assure that audio device is correctly identified/enabled?
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Realtec AC'97 Audio is what I believe I should be using
AC'97 Audio drivers are often the ones needed for on-board audio, but I wonder…
What is it that makes you think this is the correct driver for your machine?
If correct, also be sure that you install the driver for XP, and not for VISTA/win7
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Have a look at the website of your machine's manufacturer
Look up your machine by model number
Then click Support - Downloads
More than likely there will appear the correct Audio driver for your machine.
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Bottom-line about an audio PCI card, is "yes", but double-check all of the above and previous before making a purchase.