Same here. I just downloaded the Sims 2 Ultimate Collection from Origin. There is over 400GB free disk space. It's a fresh installation of the SIms 2, I only downloaded some mods. I tried the solution with the trademark sign, but there's no improvement. I keep getting the "running low on disk space" message. I have Windows 10 version 20H2.
The game is playable, but there are serious problems. First, it seems to take too much time to open and load. I can load neighborhoods, play normally and save my game, but if I change the resolution and other game settings, they dont stay the next time I open the game, so i have to change them again every time. Furthermore, custom content enablement isn't saved. I mean, when you open the game, it asks you as always if you want to enable custom content and states that you need to restart the game in order for custom content to function. That's ok until now. If I enable it and restart the game, when the game loads again the mods are shown disabled and I have to select again to enable them, but that isn't ok because I need another restart, but mods enablement can't be saved, resulting in that I can't have mods.
So it seems that the game can't save some settings and preferences.
I've searched all kinds of solutions i could find to it. I found out that most people solved it by removing the "TM" symbol from that registry entry. For me it doesn't work. So what could I do?