The original PC port is considered "abandonware" and suffers from compatibility issues on modern hardware, such as erratic physics if the frame rate exceeds 60 FPS. The community-standard solution is the Lucas' Simpsons Hit & Run Mod Launcher from Donut Team. The Simpsons: Hit & Run (PC) - Crowd Control

: Use an external USB disc drive if your modern PC lacks a CD-ROM. Install the full package to your hard drive.

Since there is no official digital download, the most secure way to obtain the game is by purchasing a physical 3-disc PC copy from second-hand retailers.