Have you tried Google Chrome OS? If not, here it is described how to run Google Chrome OS from a USB flash drive or on a virtual machine. Even you can install the OS in a separate partition with your current OS (Windows, Linux, Mac). But, since it is still under development there may be some issue with the release.
Here we have taken help of http://chromeos.hexxeh.net/ website. Before proceeding further please check that your desktop or notebook is compatible with the OS.
Desktop compatibility list
Laptop compatibility list
Now follow the guide
First of all, decide how you will use the OS. Either you can use it through VMWare or directly from pen/flash drive. Download the respective image file from Hexxeh website. I advice to go for the top most download link as this would be the latest one.
Unzip the downloaded file using any of the zip-utilities such as WinRAR or 7-Zip. You will get a image file with .img extension.
Download a small program for making bootable USB drive from here (Image Writer for Windows).
Open Windows Image Writer with "Run as administrator", then select the archive file (IMG) and choose the correct USB drive from the menu. Click on "write".
When the program finishes writing the image, restart the computer and go for the boot device menu at startup. Choose the flashdrive from the boot device list.
Now your computer will boot with the Google Chrome OS Flow build. Here you will need to login. Very first time log in to Chromium with facepunch as username and facepunch as password. Once the OS get started login to a your Gmail account. After this login your OS login credential will be changed with your email username and password.