I assume that you have an NForce 2 chipset and are using the K7nCR18D (or better) series of motherboards as I think they have integrated graphics.
Go to http://www.leadtek.com/motherboard.html
and find your motherboard, do some clicking and you should be able to find the necessary BIOS update for you.
As for me, I built my parents a computer based on a Asus A7N266-VM mobo, with the NForce 2 chipset with Integrated GeForce 2 MX graphics, ethernet, and sound. Basically the mobo had everything so I didn't have to wad out the dough for extra junk.
I installed Gentoo from their latest 1.4 Live CDs (stage 3 of course!) and emerged both nvidia-kernel AND nvidia-glx (IN THAT ORDER). ALSO ITS HIGHLY IMPORTANT TO MAKE SURE YOUR SYSTEM HAS THE COMMAND "lspci". I think the NVidia drivers use "lspci" to figure out what card you have so as to "act" appropriately. Try emerging "pciutils" that MAY have the lspci command if its not on your system. That problem almost drove me insane for my computer (Shuttle AK35GT w/VIA-KT333 chipset), but whan I realised I didn't have lspci, it all came together WHY the NVidia drivers didn't work.
I addition, if you do also have integrated network and audio, also emerge both nforce-audio (Make sure you have the kernel sound module for the nforce chipset enabled as well, I have it compiled as a module) and nforce-net. There may be a little more you have to do, but the emerge script will tell you what to do if necessary. If you decide to recompile the kernel or update to a newer one, YOU'LL HAVE TO RE_EMERGE both NFORCE-NET and NFORCE-AUDIO each time you rebuild the kernel and modules! It sucks, but that's the way it is!
I seems that leadtek has quite a few boards with integrated graphics on their NForce 2 chipsets even with Integrated GeForce 4 MX (is that what you have?).
If you follow the above, that SHOULD work, if not, I'd recommend posting to a Gentoo forum, or reply to this post.