The answer depends on the age of the CMC, where the software was installed, and which software you are using. They re-wrote the software about 5-8 years ago, and the newer version uses a database for many of the components, while the older version just saved them as individual files. The original one was called MATDESIGNER, and the newer improved current version is called FRAMESHOP. For most, it could have several thousand things saved without being any kind of issue for space. If you are just cutting something, you're probably not saving it. If it is something that you do often, then maybe you are saving them.
You can click MY COMPUTER on an older PC, or go into EXPLORER and click THIS PC on a newer computer. This will show you all of your drives, and how much free space is on your primary C: drive. If it is dangerously low, it will probably turn red and indicate this as a problem.
It's also a good idea to do a backup of your data, just in case of a hard drive failure. (Hard drives can go in a few years) This way, you'll have your custom configuration settings and previous jobs saved. It will save you a day or so of recalibration, to have this saved, if you ever have to replace the PC.
One way to recover some quick space is to empty the recycling bin.