@jordantan05 Feel free to post some screenshots of applications or other data you don't remember downloading. Or, if you know what it is and you're sure you don't want it on your computer, you can use Revo Uninstaller (the free version is fine) to remove everything associated with a given program. This is more thorough than simply uninstalling through the Control Panel.
Regardless of what data this is, you need to clear more space on C, and D is full enough you'll probably want to go through its contents sooner or later as well.