Things keep going to my SSD?

did you redirect your folders to the D: drive (your HDD)?

your Downloads folder defaults to the C: drive unless you manually move it...

It's because your Users folder is still on your C: drive. Storage drives don't actually get full because of your downloads, they just get full because of programs creating their own data files. Some of it is just temporary files, and you can free up a lot of space by clearing your temp folders. You can clear that up by running the "Disk Cleanup" app, that comes with Windows.

The more permanent solution to this is to move your Users folder to the HDD. You can follow the instructions in the link below, it shows you how you can move the entire Users folder to D: drive.

https://www.tenforums.com/tutorials/1964-move-user...

many programs arrogantly assume they belong on the boot drive, which is your SSD. in addition, Windows default download location is on the boot drive. Then, many programs arrogantly assume that they should save their files to the boot drive.

change the Windows default location. then uninstall programs that you don't want on the SSD and reinstall them to the HDD. then change the default file storage location in other programs from the C: drive [the SSD] to the HDD.

Or just buy and install a much larger SSD ... 1 Tb is not unusual these days

You probably need to change your settings for where new content is saved...

go to settings ---> system -----> storage -----> "change where new content is saved" and then set it accordingly.

I agree with keerok because when I tell Chrome to download everything to X:/Documents it won't end up on my C: drive. The same applies to manual downloads which always asks where it should be saved to. My Steam settings are different than my Origin games because they also have an option where to install and more.

One good place to find tech help is Tom's Hardware https://forums.tomshardware.com/ They do like data so you may want to be a little more specific such as where this download is originating from. Some stuff doesn't help us help you. 

Let's assume Chrome is the problem.

How to Change the Download Folder in Chrome

Select Settings.

Scroll down and click "Show Advanced Settings."

Scroll down to the Downloads section and click Change next to the Download location box.

Select a new folder and click Ok.

https://www.laptopmag.com/articles/change-download...

In order to navigate to settings, first the user would need to click on the triple dot or bar symbol in the top right of the window. 

It's either you think you're saving your download to the HDD but actually not or your SSD is too small and you've filled it up with a ton of games.