NVidia kernel driver support for FreeBSD-5.1

Hello:

I've got a PCI-NVidia Riva TNT 64 video card at home,
and I've tried to compile the drivers but it doesn't work,
and after changing the source to let the compilation progress,
when the module is loaded I've received a "kernel panic".

Im using FreeBSD-5.1 with XFree86-4.3, what can I do
to solve this issue ? I can not run the X system using
the "nv" driver, my computer hangs up.

Any help will be useful, thanks!
-- 
JFRH