kikedeolivos: the problem is that you think that drivers work like they do on Windows where they get copied into place when they are in use, and there is some frequency of getting corrupted [1]. This just does not happen on MacOS in the same way. Drivers are dynamically loaded on startup and nothing is copied into place.
If you are convinced that you need to mess with things, then here are five steps you can take:
1) Boot from your restore disks and see if the audio problems go away. The restore disks boot a version of MacOS that I bet included all of the audio drivers (if possibly a bit old). This will help you eliminate hardware problems from your list.
2) Reboot your computer with the Shift key held down. This will do a "safe boot" (does not load a bunch of things), and on 10.5 and above will also cause the kernel/driver caches to be rebuilt.
3) Look for audio related setting in /Library/Preferences, /Library/Preferences/SystemConfiguration, or ~/Library/Preferences. Wiping these and rebooting might help.
4) If none of those have helped, try installing the latest "Combo" update from Apple. This is a bit of a shot-in-the-dark solution, but if your driver file is hosed (very uncommon), and the Combo happend to have it, then it will be replaced. I should note that it is looking likely that a new point-upgrade for 10.6 is rolling out soon.
5) If all else fails then you are going to need to re-install your OS. Technically you could replace the one file/bundle that is this driver, but if you don't already know how to do this, it is probably not a good idea to go playing with it.
[1] I have never understood why Windows does this. It just encourages the driver makers to play games with writing bits to the driver files that causes the corruption in the first place. Apple's way makes sure that things can work even from read-only media, and avoids the corruption issues altogether.
