installation - Windows 10 technical preview: Windows can't be installed because this pc uses a compressed operating system

I am trying to upgrade to the Windows 10 technical preview, however when I do, it says that I can't because I am using a compressed OS. What does this mean?

My build:
Intel i7
Windows 8.1 Pro for Razer
8gb ram
1TB SSD (890GB free)

I am installing via the ISO