Delete the old licence file in %APPDATA%/HI-TECH Software/ and re-run installer. Use the command-line flag --LICENCE=free to force free mode.
Modern Windows security can block the compiler from writing temporary files during the build process. hitech+c+compiler+for+pic10+12+16+mcus+v983+download+updated
Verdict
The answer, for millions of legacy projects and industrial systems, has consistently been the , specifically the Pro edition for PIC10, PIC12, and PIC16 families. Even after Microchip’s acquisition of HI-TECH Software and the introduction of the XC8 compiler, the standalone v9.83 release remains a gold standard for stability, speed, and predictable compilation. Delete the old licence file in %APPDATA%/HI-TECH Software/