Windows users often ignore their TEMP folder. It’s a junkyard where old files (and folders) live even though the application that created them has long since been shut down. Well behaved applications keep track of the files they create there and remove them on completion of the task. However sometimes applications crash, or they just aren’t programmed to clean up after themselves.
Autodesk’s Civil3D application is known for this as well. It appears that each time the application is ran, a subfolder is created in the TEMP folder that begins with “ogs” and is followed by a series of digits. This subfolder (and subfolders thereunder) remain after the application closes normally.
First close all running applications, maybe even reboot. Next (for liability reasons) we are going to refer you to this link for the actual clean up process.
Consider getting a habit of doing this periodically, daily or weekly depending on how much you find. Also consider doing a periodic defragmentation (unless you have an SSD) to help keep your drive running at optimum speed (as Civil3D needs all the speed you can muster).