I do not need to know what is using the missing space but I am intrigued as I believe du is correct. There is only the stuff I expected on /dev/hda1 and it puzzles me to see an extra 500 MB or so missing.
It has been suggested I try adding stuff until the disk is full for df but not for du. This strikes me as risky. Is there a tool that will allow me to see what is actually using the space? Patrick