Got it solved! Based on rand_79's assertion that I should not need a driver, I went back to look through the setup once again.
Long story short, I found an IDE cable that came with the MOBO and was color-coded to match the description in the MOBO manual. I replaced the generic IDE cable I was using with the one from ASUS and "VOILA!"
The Vista Install now appears to be almost finished with the fourth "Installing Updates" step.