Writing in hopes to save somebody else time and frustration.
Hardware: stock Gigabyte MA69G-S3H, Realtek 889A audio. I'd imagine the S2H had the same issue. 4GB RAM
Installed Windows 7 64-bit Home Premium after formatting a Vista 32-bit installation. Everything was fine, except for two things:
1. White screen instead of login screen. Entering password magically worked and would progress me to the regular desktop.
2. No sound. No sound devices were even recognized. Even after installing latest drivers from Realtek website.
The solution was to go in to msconfig and in the Boot -> Advanced settings, I downgraded my max memory to 4095 from 4096.
Clearly this is a 32/64-bit issue. The drivers were allegedly the 64-bit drivers, and the OS is 64-bit, but using 33-bits of memory space seems to have totally KOd the driver. Probably the developer only had 2-3 GB of RAM or something.
I only have 4GB of RAM, so losing 1MB is not a big deal. If I had more, I'd be more upset about having to artificially limit the memory in a 64-bit system.