(as Administrator).
: Open MPLAB IDE, go to Project > Select Toolsuite , and choose HI-TECH Universal ToolSuite from the dropdown menu to begin your project. Important Compatibility Notes
: Ensure you check the box for "Add to environment path" . This allows MPLAB IDE to automatically detect the compiler without manual configuration. Configuring HI-TECH C in MPLAB IDE
You can find these legacy versions through official and community archives: Official Archive : Microchip maintains an MPLAB Ecosystem Downloads Archive