WinHelp CNT format is used to store only the table of contents for WinHelp help project that is consisting from various other files, like RTF, BMP, GID, FTS, etc. To convert WinHelp project, or document to Word DOC file you will need all project related files, or compiled WinHelp document (.hlp).
In a word, direct cnt to doc conversion is not possible.
So don't expect any so-called cnt to doc converter or cnt to doc free online conversion tool available.