System drive, OS is Windows 7 x64 SP1 Ultimate.
Windows Explorer shows 100GB of used space.
TreeSizeFree shows 75GB of used space.
Total Commander and FAR confirm TreeSizeFree's measurements (counting hidden files).
Shadow copy is using up to 5GB with the current usage of 1.36GB.
Running FAR from Win7 PE shows the same.
Checkdisk shows no bad sectors. Disk is an OCZ SSD.
SMART monitor suggests SSD condition is perfect.
Where is the rest of space gone?