A simple google for changing the Google Chrome web-browser’s UA (user-agent) string would lead you to a horribly old, yet popular result that would ask you to basically hex-hack the chrome binary [Winks at labnol.org]. Ugh, ugh, ugly for 2010!
For those who don’t know yet, you can start a fresh chrome window with a custom UA using the –user-agent command-line parameter while launching it:
# Using chrome, or chromium -- as you like it. chrome --user-agent="My User Agent String. Bow to it, statisticians. Kidding."
You can then visit http://whatsmyuseragent.com/ to verify the results of the user-agent property change in Chrome/Chromium.
The command-line parameter, –user-agent, is (not very) surprisingly not documented under the supplied manual page.