I have a new XPS L521 iwth 3rd Gen i7 and 8 GB RAM with 100 GB partition for C:
Something is using a massive amount of space on the C: As of yesterday, I had almost 40 GB of free space.
See the attached screenshot from WinDirStat.
Here is what I have done, recently:
1. Empty Recycle Bin
2. Removed unnecessary crap programs
3. Seems like I enabled a backup through Norton to go to my external hard drive destination. See attachment for screenshot confirmation
4. I was going to do a windows backup, but stopped it this morning because I have other things to do.