Squeezing disk space on C
Tuesday, July 21, 2015
You can reduce the size of the hibernation file to a minimum of 50% of the total physical memory:
powercfg.exe /hibernate /size 50
From Admin CMD shell. The size of hiberfil.sys will be reduced immediately.
From <http://superuser.com/questions/402768/can-i-set-hiberfil-sys-to-another-drive>
Follow this up by reducing the page file on C: to 500mb (or even just None) under System >> Advanced >> Performance.