I'm assuming you're asking about searching google from the chrome address bar.
You could simply type "-windows" along with your query to exlude any results with "windows" in it.
However, if you think you'll use this so often that globally excluding a keyword from all of your searches will be worth it, follow these steps:
Menu>Settings (Menu is the icon with 3 horizontal lines in the top-right corner of chrome)
Under "Search" click on "Manage search engines..."
Under "Other Search Engines" add a new entry with name set to "google-foo", keyword to anything, and the URL to
http://google.com/#q=%s%20%2Dfoo. (Replace 'foo' with the word you want to exclude.)
Optional: You can specify other words to be excluded by adding sets of
%2D are hex codes for space and
Hover over your new entry and click on "Make default"
Note: This will get you the behaviour you want, but I don't recommend step 4 because ALL searches from now on will exclude those words. Instead, set the keyword to 'wg' (or something else short) and use it as follows in the chrome address bar:
wg query goes here
This will search google for "query goes here -foo" which will exclude all search results with the word "foo" in it.