CalibratedSoftware has plugins to allow EX video to be viewed in Quicktime in non FCP systems (both Mac and Windows). The trials have an ugly gray band in them but you can test to see if it'll work on your laptop before buying.
VLC will also play the clips but won't read the time code.
I think a G4 is not going to be up to the task of playing EX clips. When I first got the EX1 I was still using a G5 desktop and even that struggled a bit when editing although it did play individual clips cleanly.
I think you're faced with getting a new Intel laptop. There's no way around the G4's power limitations.