I don't know if your problem is related to Windows not seeing the new card, but... a word about the Kyro chipset.
I don't think the Kyro chipset is the best choice for AH. That chipset doesn't support the DirectX Transform & Lighting instruction set, and that's what probably results in a big frame hate hit when players encounter smoke and special lighting conditions (for example sunsets).
I read a post here weeks ago by a guy with the KyroII-based Hercules Prophet 4500, and he wasn't happy.
In some conditions, the Kyro II performs better than a GeForce2 MX, but in others, it doesn't (that lacking T&L instruction set), and you're talking here about a Kyro I-based card. And some people consider they have low frame rates with the MX400.
The Prophet 4000XT is a low-end video card. I don't think you can expect much performance from it.