You have to install the propriatory Nvidia drivers. They are aviable from the same place as the video drivers. The "nforce" drivers... I don't think they make a distiction between nforce and nforce2.
Nvidia doesn't realy allow these distros to distribute the drivers allong with the OSes, and they don't help developers develope open source versions of it.
They work, but I don't like that. Sold my nforce2 chaintech board and bought one with a Via kt400 chipset. Hopefully that board is more Linux-friendly.
But the drivers from Nvidia DO work. If you need to use the onboard Nic to connect to the internet, you have a bit of a chicken and the egg problem, since their is no linux nic drivers for most nforce boards. So download and put them on a CD or floppy (if it fits) before you begin the Mandrake install.
The nvnet is the module for the Lan, also their was a agp driver, too.