Make sure that your kernel matches your kernel source:
uname -r should be the same as
/usr/src/linux- "uname output"
also in Mandrake 9.2 there may be a soft link called linux in /usr/src/ this should point to the directory named after uname -r
finally mandrake has agpgart compiled into the kernel, depending on your kernel version agpart might not be compatiable, you can force the card to go around this with the option:
Option "NvAGP" "2"