At least when you've got any docs in .CHM format in the folder tree.
If you drop a file called CSharpDocs.chm into a folder:
\toplevel\C#\docs, you can open it, but it won't display. The #
anywhere in the folder hierarchy is enough to cause problems.
I spent quite a while trying to figure this out. Tried it on several
systems. Even discarded some CHM files, thinking they were corrupt.
This is evidently a problem with Microsoft's own reader, hh.exe. I
haven't been able to find a fix. Well, aside from renaming things.
You'd think that Microsoft would have some inhouse C# docs in chm
format?
On a different tangent, you can't name a file or folder .NET_whatever
either but of course that's a file system problem. I suppose everyone
is doing the same as with the #...just spelling out DotNet.