audio driver destroys itself

I have Windows XP on a Latitude D610 and the audio only works when it wants to. I have to reinstall the audio driver from R99254.exe, and usually this works to restore it. However, recently it has been saying that the installation won't take effect until my computer is restarted - but when I do restart it, the audio doesn't work. I get the same message when I reinstall the drivers, as if I didn't just install it five minutes ago. Before this happened, for about a week the audio would only work if I installed from this same file, and it said that my audio drivers had been updated and it worked fine. Then it wouldn't work after a restart. The computer thinks that all hardware devices are working just fine, and rolling back the drivers doesn't work either. Any clues on what might be going on?