If your model is old enough, you can find Mac OS 8/9 drivers on the HP website.
As for Schematic Capture, the only things I could find were McCAD and Designworks Lite. I can't seem to find a copy of the 30 day demo for Designworks anywhere. (Found a couple in binhex format, but they wouldn't decode.) I'll take a look and see if I can find it on a MacAddict CD.
Edit: Found a copy of DesignWorks 4.0.1 on MacAddict Disc 26. (Which I assume turns into "Lite" in demonstration mode.) http://www.mediafire.com/?q04ubax2iubmk0z