You're using the Aspyr update for TSL. That's not compatible with the old exe. You'll need to switch to the "legacypc" version under the Betas tab. Right click on the game in the Library list -> Properties -> Betas, select legacypc from the drop-down menu. This will involve redownloading some of the game assets, so any mods you already installed will be nuked. If you have installed any mods, you'll want to delete your Override and Modules folders, then from the Properties menu go to Local Files -> Verify integrity of game files. After all that is finished, you can replace the exe with the WS patched one.
That said, the Aspyr version should have native widescreen support anyway, so patching the exe is unnecessary. But the Aspyr version is full of bugs so it's not worth using unless you absolutely must have achievements and/or controller support.