The original game may have issues with widescreen resolutions or high frame rates on modern hardware. Most players use a to fix these:
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. 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. The original game may have issues with widescreen