Unable to open Sims 4 in Windowed Mode

@Kazuzi3  If you'd like to troubleshoot the issue, please run a dxdiag and attach it to a post.

https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/

If you ever forget to switch back to fullscreen, you can set the fullscreen value to 1 in options.ini, which is in Documents\Electronic Arts\The Sims 4.  It'll switch back to 0 when you change to windowed mode in-game.

I've attached the DxDiag. I think it might be worth pointing out though that this is the second computer I have had this issue with. This computer and the computer where I also had the issue are both made by Dell (I can't access the other computer anymore to get any information from there unfortunately). I also ran the Sims 4 on an Acer laptop in between running it on the two dell computers and never had the issue with the Acer laptop. Don't know what's different about those two, but it might be something that could help.

Ok, so I did some playing around and decided to try to uninstall some of the preinstalled stuff from Dell. I tried it first without uninstalling anything just to pretty much test that the problem still existed, and it did, but what I did notice this time was that the audio was still playing despite the screen being blank; I usually play without audio, so I never noticed this before. The first thing I uninstalled was Alienware Command Center. The startup issue still occurred after uninstalling Alienware Command Center, so I know for sure that wasn't the issue. The next thing I uninstalled was Dell Cinema Guide. Somehow, that fixed it. I even tried closing and restarting Sims several times since sometimes it would open and sometimes it wouldn't. It ran every single time. So for whatever reason, Dell Cinema Guide seems to have been the culprit. I have no idea why though.

Ok, Scratch that. The problem is still occurring even now that all of the preinstall Dell and Alienware items have been remove from my computer.

@Kazuzi3  Did you try playing in a clean boot with nothing else running in the background?  It's still worth trying.

It worked with the clean boot, but then again it also worked after I reenabled all of the same things I had enabled before and restarted my computer after the clean boot. It's not really a consistent thing, which is why I'm finding it so hard to figure out what's wrong and probably why I still haven't figured it out after multiple computers. I might play around with it some more, but I can't always guarantee I find what fixes it because sometimes it works and sometimes it doesn't.

@Kazuzi3  It's possible having some other program open interferes, but only sometimes, for example the Discord overlay could be finicky to work with.  If you're interested in continuing to poke at the issue, it might help to keep a list of everything that was running, and any relevant settings or open windows, from each time the game didn't open.  And since you can just edit options.ini to launch in fullscreen mode, it's easy enough to get around the problem at any given moment.

If you do ever figure out what's causing this, I'd be curious to know.