Both solutions require running game from AvP.exe (enforces DX9). Fullscreen: SoftTH (DX9 x86). In-game select massive resolution. OR Borderless: Shortcut/launcher argument -subwindow. ShiftWindow (+ border = borderless). Optional FOV (not needed, recommended): Use FOV Changer *

(PLP screenshot with bezel effect)
Game looks great DX9, all rendered perfect. Sad DX11 game won't spread windowed (abnormal).
* FOV Changer:
Run it from any folder. Enter preferred FOV, click Set & Enable & DX9. Bind to e.g. F12, trigger in-game. When FOV reverts, repeat (rarely).
Predator's FOV is bit weak, ~75 is better (stock ~69). Alien's FOV bit strong, ~82 better (stock ~88). Marine's stock FOV great as-is. Download: http://community.pcgamingwiki.com/files/file/490-aliens-vs-predator-201….

(Marine view, FOV stock)

(Predator finisher, FOV 75)

(Alien view, FOV 82)

(rendered video)
View guide for general help with the instructions.