Docker Desktop for Windows uses WSL to manage all your images and container files and keeps them in a private virtual hard drive (VHDX) called ext4.vhdx.
It's usually in C:\Users\YOURNAME\AppData\Local\Docker\wsl\data
and you can often reclaim some of the space if you've cleaned up (pruned your images, etc) with Optimize-Vhd under an administrator PowerShell shell/prompt.
You'll need to stop Docker Desktop by right clicking on its tray icon and choosing Quit Docker Desktop. Once it's stopped, you'll want to stop all running WSL2 instances with wsl --shutdown
Mine was 47gigs as I use Docker A LOT so when I optimize it from admin PowerShell from the wsl\data folder