Weirdness with network card detection and installing drivers.

I've got a Shuttle mainboard with built-in NIC.

Here's where it gets weird:

Installed SLES 10 SP2 64-bit. It founds the "Marvell" NIC and it worked
just fine.

I had some other issues, so I whacked the install and re-installed with
SLES 10 SP1 32-bit this time. Still found NIC, worked just fine.

I discovered I needed XP on the machine to apply BIOS updates, so I
whacked the partitions and installed XP, Nvidia drivers, etc. NIC works
fine in XP. Updated BIOS, rebooted. XP still works fine with NIC.

Now I installed SLES 10 SP2 32-bit this time. This time around, it
found the NIC, but found it as nvidia MCP. Driver did not work (no
network connection).

Whacked install and put SLES 10 SP1 32-bit on this time. No driver
found at all.

If i probe the hardware via Yast, it sees the onbobard ethernet, but on
the Network module, it shows nothing.

If I go into Yast to select modules, neither MCP nor Marvell are on the
list.

Questions:

1) Why would it find the driver "differently" or not at all on
subsequent reinstalls (I deleted the partitions every time)

2) Why would it have "built-in" drivers, but those don't show up on the
list in Yast if you wish to manually add one? Can you only install
network cards upon the initial install?