Often on sale for a few dollars, the Return to Castle Wolfenstein Steam page includes the single-player campaign and is compatible with modern Windows.
The most popular source port. It improves performance and stability on Windows 10/11. download-return-castle-wolfenstein-apun-kagames-exe
Install the game via Steam or GOG, then download the ioRtCW files from GitHub and place them in your game folder. Often on sale for a few dollars, the