I also use a sis900 which is integrated into my ASUS mainboard.
Try modprobe sis900
and can you load other modules?
You may need new modutils (2.4 kernels) or mod-init-utile (2.6 kernels)
I don't think you are screwed.
I was able to get mine working with 2.6.6 2.6.7 and 2.6.8 kernels using the sis900 module.
find the option in networking -> 100MBPS Fast Ethernet or something
I can't get /dev/eth0 to appear.
stat returns no such file or directory
what are the major and minor numbers for mknodding eth0?