I think the Core Duo isn't going to come out being targeted for PCs. It's mainly a laptop CPU, somethign to compete against the Turion64. It's just a back-and-forth relationship in the notebook world. Intel dominates with it's Pentium M CPU, then AMD releases it's 64-bit notebook CPU, then Intel launches it's dual-core notebook CPU...see where this is going?
Anywho, although the Core Duo is in Socket 478, I DO NOT suggest you purchase it. It's a notebook CPU, not a desktop CPU. Although it may fit your old motherboard, I don't suggest that you purcahse it, instead, get a Pentium IV processor in Socket 478.