If lsmod doesn't list the nvidia module then it's not loaded. You can try to manually load it by using /sbin/modprobe nvidia.o .
lsmod should return a list of modules. (lsmod is list modules). By returning nothing did you mean no nvidia or nothing?
I think mandrake uses /etc/modules.conf . The line I mentioned for that file autoloads nvidia on system startup. You might check to see if it is in modules.conf .