This is public service announcement for anyone banging their head against a wall trying to get audio on a Gateway MX6445 that has Vista 64bit OS installed.
There isn't a driver.
I've just spent a week googling every answer, and communicating with Gateway tech support. I download just about all of the 64-bit audio drivers they have, and tried to install them, unsuccessfully. They simply don't have a driver, and they're not working on one.
So why would Gateway sell you a computer with a 64-bit processor, but yet fail to provide you with 64bit drivers? Beats me. Just keep it in mind when it comes time to upgrade your laptop.
If this situation changes, I hope someone will post an answer in the comments here.