I bought an SSD (SandForce 2), created a tiny 25GB partition on it for Windows and installed Windows 7 64-bit. In order to free disk space, I enabled compression on the drive using the Properties entry in the context menu for the drive in Explorer.
Prior to compressing I had around 5GB of free space. After compression I had 4GB, so compression was not working for me. I figured this might have happened because of the built-in data compression of the SSD.
I decompressed the files again - after decompression, it left me with 7GB of free space! Better yet, after restarting, I had 10GB. What is happening here?