There is a known bug with Mandrake 10.0 "official" and NVIDIA video drivers. Try using 10.0 "download version" or the earlier release "Community download". They both work OK with my Nvidia FX5200 128 MB (AGP 8x).
10.0 Official CD set (cost me $70) was not able to successfully work with my video card, no matter what. The problem is the Official kernel 2.6.3-7mdk - at least that's what NVIDIA's install told me. On the other hand, a visitor to Mandrake Club says that the problem is in the XF86Config-4 file, and he offers a workaround. I have not tried that yet.
Hope this helps.
<< have a look
5/1/2005: I found out that my motherboard was the cause of most of my problems with Mandrake, etc. It was a SOYO SY-K7MMP2, and I replaced it with a Giga-Byte GA-7N400-L. The motherboard was the ONLY thing I replaced so it was definetly the culprit.