Let me get straight to the point. After around an hour and a half of playing the game, I accidentally went into windowed mode. After that, whenever I attempt to go into fullscreen mode, I get the message "Failed to set requested screen resolution of 1280 by 800, 16 bit color, fullscreen. Restored to safety settings of 800 by 600, 16 bit color, windowed.". This resets it nigh instantly to windowed mode and a 800 by 600 resolution. Not only this, but If I set the resolution higher I am incapable of seeing the entirety of the game, making it unplayable. Does anyone know what I could do to help with this?

Windows 7 user here, but i tried to reproduce your problem. I, too, got the same error message. I noticed one thing however: if my refresh rate was set to 60Hz I would get the error message, but if I set it to 75Hz, it would accept the 1200x800 resolution and go fullscreen without any problems. Can you try this?

I tried this, but when I attempted to do so, a little box without any options on it came up. Am I simply being an idiot? Or can I not change it for some reason?

If you select 800x600 res, do you have the option to change the refresh rate? Could you post a pic?

No, I cannot. I have attached the picture you requested

Thank you for trying help! I'll probably end up posting a solution here for posterity, so if you know anyone else with a problem you may want to redirect them here.