The ethereum blockchain is more than 50 GB, so it`s not ideal to have it on your C-drive when you have a small drive like a SDD.
The best practise to free up space is to move it to another drive and create a symlink.

Run DOS (cmd.exe) as Administrator and run the following commands

cd C:\Users\[user]\AppData\Roaming\
mklink /D Ethereum D:\Ethereum