If the latest drivers are installed EXACTLY as they should be (there is a 2 page instruction on www.nvidia.com ...), it's most probably the motherboard/bios that's bushing the breakes here. Check your bios settings for any AGP related subject and make sure it is set to maximum or enabled, depending on Bios.

Besides, the MX card is not exactly cutting edge technology. This will be the real minimum ...

Cheers - wolfgang