Re: How big is the latest update?
@impstrump If you're still using Origin, or you can reinstall it:
Origin has a Move Game function when you right-click a game in your Origin library. Then you just choose the folder on D you want to use, and Origin does the rest.
If you can't run Origin anymore, and some players cannot, you can cut and paste the Sims 4 program files to D, then tell the EA App to install to that location. The App should verify the presence of those files instead of downloading everything again.
Even if neither approach works and you need to uninstall and reinstall the game, this shouldn't affect your saves, which are in Documents > Electronic Arts > The Sims 4. Still, it's a good idea to back up this folder, now and in general, so you're protected if anything happens to your data.
By the way, you could simply move this folder to D instead by using a symbolic link:
How much this helps with the free storage issue will depend on how large the folder is, obviously. To see the size of the folder, right-click it and select Properties > General.