I actually had a lot of issues with my Steam Version and never got the Game running properly, many others did find fixes but only due to other users.
For widescreen and Multi-Screen you can look to
WSGF = Wide·Screen Gaming Forum
WSGF users have created several options including Multigame Tools. My recommended Order of Preference is
Flawless Widescreen v1·0·15
Widescreen Fixer v3.4 r716
Universal Widescreen (UniWS) Patcher v1·03
Different Tools work better for different Setups and I have 7680×1440 (3 of 2560×1440) Eyefinity.
Though I'm happy to get this Game running on a single Screen and WSGF Forums are great help sources
Flawless Widescreen is my goto tool and even brand new games require attention, it only has Games on it if issues occur latest
The Vanishing of Ethan Carter - Typical issues associated with Unreal Engine
The Evil Within - A number of issues
Middle Earth: Shadow of Mordor - Issues with letterboxing, Menu FOV and HUD
Alien Isolation - HUD Problems on Nvidia Hardware
Star Wars - Knights of the Old Republic was designed for specific resolutions eg. 800x600 - 1600x1200, when attempting to modify it for higher resolutions or even widescreen resolutions many problems are introduced.
This fix injects a custom C++ DLL that dynamically creates new GUI files based on the active display resolution and new TGA background art, additionally it fixes the cutscene black bars and missing text on some resolutions, it's not perfect but it's a start.
NOTE: You must start KOTOR and exit atleast once before this fix will properly be active, this is because custom files generated need to be detected by KOTOR before it starts, additionally graphics backgrounds and GUI files will not be generated unless you change the resolution Flawless Widescreen Widescreen Fixer Star Wars: Knights of the Old Republic | WSGF