If you take a completely formatted (empty) 128 GB C drive and install Windows on it (any version, let's say 8.1 in your case), it's not going to take up the entire drive. I have no way of knowing what else you may have installed on it or what is taking up so much space without poking around at it or running routines like Disk Cleanup.
And again, you may want to look up or get some help with checking out how many Restore Points you have. Those can take up a lot of space, or dozens of GB anyway. Personally I run with System Restore totally shut off because professionally I've found that malware can hide in the Restore Points. Different users' experiences with them will vary.
