Is that they are not Digitally Signed with M$ so if you have XP and attempt to install the driver the computer may Blue Screen of Death out and reboot. Here is M$ official Error Message when this happens
[b][i]Problem caused by Windows (R) WDM driver for Realtek AC'97 (ALCXWDM.SYS)
This problem was caused by Windows (R) WDM driver for Realtek AC'97 (ALCXWDM.SYS). This program was created by Realtek Semiconductor Corp.. Realtek Semiconductor Corp. does not currently have a solution for the problem that you reported.
Recommendation
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For support information and product updates, Realtek Semiconductor Corp. recommends that you go online to the following website:
Realtek Semiconductor Corp.[/i][/b]
I only ran across this recently whit a loaner that I had returned apparently the Sound worked OK when it left here while the customers Sound Editing Computer was in for repairs but when it was returned there was no sound. Apparently he had removed the drivers to use some external Sound Device and when I attempted to reinstall the Realtek Drivers the system BSOD and rebooted. You can try Realtek latest drivers but they didn't work for me.
http://tinyurl.com/zlc2q
Appoarently some XP Hot Patch has caused this to no longer be possible to install these drivers. Very Vista like and would seem that M$ is attempting to integrate several of Vista's features into XP.
If you have a desktop that you are editing on disable the AC97 and fit a Sound Blaster Card and install the drivers for it, you'll be rewarded for going to an Industry Standard Sound Card.
Col