It sounds like you are using either a 10.2 install CD from another system or the universal install CD.
Seeing as the iBook 800 was released after the release of 10.2, the standard 10.2 install media doesn't have the drivers needed to drive your system.
If you no longer have the original 10.2.x media that came with your iBook, then your best course of action is to find 10.3 media.
Or you could try running the 10.2.8 combo updater to see if it installs the drivers for your graphics card. I'm not sure that those were included in the updates, but it wouldn't hurt to try.