I use the same manufacturer of audio, the realtek HD audio, designed for vista, and running XP now... I had the same issue at first, the audio did not work... It would work with some things and not others; This is what i did to fix it..
1. Go to "my computer" right click and select manage
2. locate the device manager
3. find the hardware, (likely under audio)
4. Right click and select uninstall
5. close out box's
6. Go to your add/remove programs box
7. Uninstall the drivers and utilitys
8. go to google and look up the drivers you need for your card, there are two versions for mine, one is 1.88 and the other 1.91. I used the newer version and that fixed this issue.
9. once you have the new drivers,
9-1. Note: if you use IE i can help, if you use firefox your on your own-
9-2. You will need to open IE and select Tools, internet options,
IE7 you can just click the advanced tab and select Reset... this will revert you back to factory settings..
9-3 if you use a toolbar as in Google or yahoo, you will need to remove these, and also remove them from your registry as well, as all the addon's get stored there, as well... I would recomend not reinstalling them due to this fact... (If you get a browser highjack with google toolbar, or yahoo tool bar,you will have added nightmare steps to remove it) Note: I take no respondsibility for you editing your registry...
10. Reboot the machine
11. you should get a prompt that states new hardware found
12. install the new drivers, make sure you get the full package software, as it is needed if you want true HD audio (the drivers and software).
13. Once the drivers are installed, install the software if you have not done this already.
14. reboot machine
15.... You should be good to go....