If you do not use, or intend to use hibernate mode:
I had disabled the hibernate option from my Start menu, but the file was still there. The command below removed it.
Sizes may vary, but search for "hiberfil.sys" in the root folder. I couldn't see it (despite hidden files and folders being viewable), but Treesize saw it as a 5.5GB file.
A simple command (remember to start CMD in admin mode) - powercfg /hibernate off
and that's 5.5GB gone.