Whenever I play this game on fullscreen mode, it does go full-screen, but a portion of the left side of the game doesn't show up. This makes me go into the non-fullscreen mode to check/uncheck a few options since the leftmost checkboxes on Options don't show up. Can I make it that fullscreen mode takes up all the screen and show all of the menus/screen? I'm running on Windows XP if it matters.

This isn't a "problem" persay; it's caused by your video card and monitor. When it changes display modes, the refresh rate changes as well, and so your monitor adjusts itself to the new display - which, forces part of Soldat off-screen.

Try adjusting your monitor's display settings (you have to do this physically if its an old monitor, some new ones have an "auto set" function) while in full-screen mode.