Various people were looking for the .chm version of the undocumented (when this .chm file
was made) structures and functions in ntdll.dll
for some reason.
Well, I happened to find it; and as it turns out, the "Undocumented Functions by NTinternals
" document (written by Tomasz Nowak) may be freely copied, modified, used, and distributed. I didn't determine why the .chm file was discontinued, although a number of structs and a few functions were missing (dead links in the .chm index), but I think it must have been due to T.N. dropping any further work on the .chm version when MSDN adopted DocExplorer and WinHelp2 for everything.
I made an effort to fix the dead links if I could. About 6 have question marks now to show that a file should be there at the link but isn't, but the rest that were missing I managed to fudge. So the .chm has been recompiled with mostly the circa 2001 files, a few of what I think were probably newer files that didn't make it into the original version, and what I could bean myself.
The file is at the following link, if you want to download it. The MSDN library version released in 2008 still doesn't have a few things documented that are in this .chm; and the Windows SDK doesn't have that info either, so it might be worth looking at.