The game natively maxes out at 1280x1024. To get proper widescreen:

Running on Windows 10 is possible but requires specific workarounds because the game's original copy protection (SafeDisc) and early DirectX 8 architecture are not natively supported by modern Windows versions. Essential Fixes for Windows 10

Check and select Windows XP (Service Pack 3) . Check "Run this program as an administrator" .