Install Chromium OS, but not from a USB

From Download Chrome OS VMWare image :

After Google announced the availability of the Chrome OS / Chromium OS source code, one of our engineers (Jon Ursenbach), immediately got to work on compiling the code, trying to see if he could get an instance of Chromium OS running in a virtual machine.

He was finally able to do it! You can download a copy of the virtual machine to use in VMware, VirtualBox, and on a USB drive here (300MB compressed / 700MB uncompressed, registration required)

EDIT

See this article:
How To Install Chrome OS Into Hard disk Alongside Your Existing Operating System.