You'll likely need to track down a used physical copy or check abandonware archives.
Since the game is from 2008, it may require compatibility patches or community fixes to run smoothly on Windows 10 or 11. Resources like PCGamingWiki provide guides on fixing inferior graphics or missing reflections in the PC version. 2. Pure (Assetto Corsa Weather Mod)
To play it legally today, you generally need to find a physical retail copy (DVD-ROM) through sites like Amazon or eBay .