Even with a clean , you will encounter issues. Here is the fix guide:
Launch the game using Warcraft III.exe . , or it will auto-update to Reforged . Key Features of Version 1.31 1.31.0 Patch Notes - Warcraft III - Blizzard Forums
Warcraft 3: The Frozen Throne remains one of the most iconic real-time strategy games in history. Version 1.31 stands out as a special milestone for the community because it was the final major patch before the release of Warcraft 3: Reforged. Many players seek this specific version to preserve the classic gameplay experience, maintain compatibility with custom maps, and continue using popular modding tools. Warcraft 3 Frozen Throne 1.31 Download
For many fans, downloading 1.31 is a way to preserve the game's original soul. It represents the pinnacle of the classic engine's development, offering features that were later removed or altered in the modern Battle.net version.
Unlike older versions that stretched the 4:3 aspect ratio, 1.31 introduced native 16:9 widescreen support, making the game look crisp on modern monitors without distorting the UI. Even with a clean , you will encounter issues
To prevent the game from automatically updating to Reforged: Do not connect to official Battle.net servers in-game.
This is the last version of the game that retains the original, classic main menu, user interface, and custom campaign features before they were altered by the Battle.net integration for Reforged. Key Features of Version 1
Right-click the executable, go to Properties > Compatibility , and check the box for "Disable fullscreen optimizations." Conclusion
Native 16:9 support that didn't just stretch the image but expanded the field of view.
Complete Guide to Downloading Warcraft 3: The Frozen Throne Patch 1.31