My System partition suddenly filled and I lost all restore points and nearly stopped altogether. Using Easeus Partition manager I extended the C drive by taking space from the Data partition. I used TreeSize and found a massive file in my user /app data folder - a Google Earth Unified_Cache folder of over 40 Gigabytes. I managed to delete it and now have plenty of spare space. I record this for comment - how could this massive cache have happened? I quickly created a new restore point but could have had a disaster.