I changed the resolution, and now I cant play the game

 So i went into the settings and  and i changed the resolution. When i did so the games screen went black and it didn't recover, so I closed down the game with the task manager, then i started it again. I went to the settings and changed the resolution a bit lower, and the same thing happened as it had before, so I closed it with the task manager again. But when i went to start up the game again the resolution of my desktop went haywire, and everything became all scrunched up and the games splash screen didn't show up, but the game was still running, and I could mouse over the the Icon on the taskbar, and I could see the window when i did so, but the splash screen was only a sliver, and nothing happened if I left it. After that, I found a post where it told me to modify the resolution in the files. I tried that and it didn't help with anything, so I could use some advice, please.