I recently reinstalled The Sims 2 on my laptop after going awhile without playing it, and I've naturally been trying to reinstall some of the mods and CC I typically use. However, I've been noticing that after I close the game and start it again later, a portion of the CC I downloaded disappears. Not all, but a significant amount. I saw it first happen the second time I opened the game a couple days later after I first reinstalled it. At the time, I thought I was going crazy and maybe just remembered it wrong. So I went back and reinstalled some of them with a shrug.

But now, I've opened up the game again, and even more CC is missing. I know it's not just me this time because a family that I made the last time I played is now suddenly wearing Maxis replacements for CC that they were wearing, and their house suddenly has blank walls in lieu of the custom walls that I was using. It's as if the game is corrupting the files and deleting them. I'm very confused, I've been playing this game for years and have never had this issue arise. This isn't even the first time I've played the game on this computer, but it's the first time that this issue has happened on it.

I'm playing this game on a 3rd Generation Microsoft Surface Laptop running Windows 10 (full specs are attached below). Any help here is appreciated.

Firstly, check that you don't have cloud storage (One Drive for example) synching your Documents/EA Games folder. Also check that your antivirus is not quarantining anything from that folder.

Wait, that might be it. Brief backstory, the last time I uninstalled the game I shoved my downloads folder into my OneDrive so that the next time I was ready to pick the game back up I could just drop my mods into the new game without having to download them again from scratch. It only sorta worked, as I think it was missing a lot when I did it upon reinstalling.

How exactly is this diagnosed and how do you fix it?

Uninstall it or disable it, its bad news as well as being crap, it deleted some important documents off my PC. If you want to have cloud storage you are better off getting something like Google Drive or Dropbox.

I've had this happen, and it was definitely my One Drive. I wasn't even using it for storage purposes, I had just agreed for my new laptop to sync with the last one, without really knowing what that would do. I turned on my old laptop ONCE to get a few old filed I needed, and next time I tried to play the sims, all of the files were merged, some were missing, duplicated, it was a whole mess! My game wasn't recognizing the files correctly.

I would also recommend to disable your One Drive or to just delete it, like I did, and then you can see if your files stop going nuts, and they're alright, you can continue adding your CC without fearing it'll disappear.