Lappy: 23Gb free from 147GB on an Intel SSD
Desktop: C: 1.2TB free from 2TB D: 1.3TB free from 2TB, coincidently I had just swapped from 1TB HDDs to 2TB ones
Server: 8TB free from 16TB
After using the lappy with a SSD and it being blisteringly fast I am planning on putting SSDs in the desktop.
Steelbeasts is my most used "sim", on the lappy it opens in seconds, from selection of mission to being on the map is around 2 to 3 seconds, the desktop is still thinking about which folder the mission is in never mind opening it

Remember the second law of Hard disk dynamics: Data will expand to fill all corners ...