I use SumatraPDF for viewing .chm-files and for the most part it works fine.
But with this file: http://www.watt-32.net/misc/vs6.chm
the left sidepanel (topic panel?) is not shown.
I MS’ helpView, it looks like this:
Also looks fine in KchmViewer (but that program is very slow). I prefer SumatraPDF.
The VS6.CHM is pretty old (from 2002). Maybe that is related?