as you said: Mandrake+Nvidia=Headaches
well Mandrake 10.1 to be more specific

if you stick with kernel 2.6.7.3 you will be able to install nvidia without a problem
also the very latest driver doesn't necessarily mean the best
depends on your hardward - i would try a few and test it with glxgears
update: be sure you edit the XF86Config-4 or Xorg.conf accordingly
substitute nv by nvidia
If you dual boot (ie into an nvidia-kernel and a non-nvidia-kernel)
Be aware that Mandrake has the annoying habit of reditting nvidia back to nv
(which is a safe precaution for newbies - cos a non-X environment would freak them out)
so yeah best to stick with 2.6.7.3 with nvidia - until someone fixes the problem
or play/experiement with the myriad of free distros
(if you got the time and patience of course)