The 100$ (percent) question is why is my disk usage 100 percent. There are now thousands of prior discussions. I usually tackle it by sorting what app uses the most.
In half the cases at the shop, it's a failing HDD and the 100 percent is due to Windows spending all its time retrying reads.
I still have 1tb of storage left on my drive, and my recovery one is empty, so how come the disk usage is so high when I try to do simple things? What can I do to fix it?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic