iCab installed on the iBook, browsing is now up to par, but the ethernet port seems to be broken - switch light flashes green instead of steady green.
Getting DivX to work with TT's tutorial, updating software using the list at pure-mac.com - OldVersion.com is useful only for Windows software.
Update: Upgrading to Quicktime 6 broke DivX playback. Downgrading to QT 5 involved first removing QT6 and then installing QT5. Removing software on the mac = dragging all associated files to the Trash. Used Sherlock to find files with 'Quicktime' in their name. DivX works with QT5 and the 3ivX codec using DivX Doctor, but files with resolution 720x480, for example, play at some 10 fps, probably because the processor can't keep up.