perhaps you refer to the fact that all the 'visible' folders and files only add up to 50GB? and your file manager reports a full drive?
that wouldpossibly be hidden files + pagefile settings, which are generally not shown in 'zombie mode' (non-admin with no file view permissions).
solve this by: open file manager > (almost top left) organise button/tab > folder and search options > view tab > scroll down and un-tick hide system files etc.
now all those hidden files visible for you to add up.
windows likes to manage your pagefile and puts it on your c drive. you can change this setting to free space by: control panel > system > advanced system properties > advanced tab > performance button > advanced tab > virtual memory CHANGE button > move default location or set your own.
if setting your own pagefile size, it is recomended to be twice the size of your RAM plus VRAM. eg 8GB RAM and 4GB 1050ti = (2 x 8) + 4 = 20GB