The least information that's needed is the audio device you're looking for a driver for. A driver is device specific. So unless you know the make and model, nobody can help.
Now once you know that information there are 2 possibilities:
1. You can download a Windows 2000 driver somewhere. Problem solved.
2. You can't find a Windows 2000 compatible driver. That's the interesting case.
In case no driver is available you've got several options:
a. Find an audio device that comes with a Windows 2000 driver. Install that in place of the current one. Problem solved.
b. You can't find any Windows 2000 compatible audio device anymore (not even on eBay), although they surely did exist 10 years ago. That's the interesting case.
In case you can't find any compatible hardware, you've got several options.
1. Upgrade to a more recent OS that supports your hardware and find a more recent (version of the old) program to access that old files.
2. Run Windows 2000 in a virtual machine on that more recent OS. While inside that virtual machine to run that old program you probably won't have sound, but in all 'normal' situations you have. If that old program doesn't need the sound (you didn't tell), this would probably fulfill your requirements.
I run Windows 2000 on a Dell Inspiron 1720 (in order to excess files created on an old program). I am searching for an Audio Driver. Dell only offer one for XP or Vista, and neither are compatible with Windows 2000. I would appreciate advice on this. Thanks.