When generating the Spring4D documentation at https://spring4d.4delphi.com/ using Documentation Insight by DevJet, I got this error:
HHC6003: Error: The file Itircl.dll has not been registered correctly.
Microsoft HTML Help Compiler 4.74.8702
Solving it turned out easy:
regsvr32 "%ProgramFiles(x86)%\Documentation Insight 3\Compilers\CHM\itcc.dll"
I got there via [WayBack] HTML Help FAQ – Wiki.HelpMVP.com:
“HHC6003: The file itircl.dll has not been registered correctly”
This error effects only a small number of users. A HH component (c:\windows\system\itcc.dll) did not get installed or registered correctly. If not installed get the DLL from another PC containing Workshop. To register the DLL run
regsvr32 c:\windows\system\itcc.dll (this path may be different for your PC – eg. c:\winnnt\system32).
This fix was originally reported by MVP David Liske: [WayBack] http://www.mvps.org/htmlhelpcenter/itircl.htm
–jeroen