The installer cache is normally very large. Deleting it isn't usually a good idea. Your Windows directory is a bit higher than what it should be, but that's likely due to how long the system has bee around.
Download Patch Cleaner and run it. It may take sometime for it to finish. Once it does select Delete to remove orphaned and superseded patches. I have a feeling you will clean up around 30GB.
PatchCleaner