Keep running out of disc space on Windows 10

My Dell PC (Windows 10) keeps running out of disc space. Two months ago I had 13 GB free. Today I have 86.2 MB. Note that I haven't installed any programs since then. I didn't always have this problem, something's definitely changed.

I've tried disk cleanup, but the only files that can be deleted account for like a couple dozen KB total. I've already moved all my word docs, videos, and images to the D drive, but still, the C drive keeps running out of space.

I'd appreciate any advice that isn't "get a bigger drive"/"get a better computer". What's the point of getting 1T drive if by all indications it'll all just disappear sooner or later? I don't want to kick the can down the road. I want to solve this once and for all. And unfortunately "buy a better PC" isn't an option either.