While trying to run Sandcastle , I faced with two errors while building the documentation. Errors on Sandcastle Help File Builder HHC6003 : error : The file Itircl.dll has not been registered correctly. HHC6003 : error : The file Itcc.dll has not been registered correctly. For some reason on my Windows 7 system, these dll files were not registered. Then, I found these files(you can download as well) and copied them into my C:\Windows\System32 directory and register them via command prompt. Run the following commands from Command Prompt C:\Windows\system32>regsvr32 itircl.dll C:\Windows\system32>regsvr32 itcc.dll That's it, now I have my .chm for my project documentation.