i'm using swiftfox for a web browser.

using about:config i changed the string:
general.useragent.extra.firefox
to
Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3 (.NET CLR 3.5.30729)

but when i go to whatsmyip.org/more it lists my user agent string as:
HTTP_USER_AGENT: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.3) Gecko/20100405 Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3 (.NET CLR 3.5.30729)

it sees the Windows part changed in the string, but it also still sees i'm using X11 / linux i686
is there a file somewhere i can modify so that i can mimic the reporting of a MS Windows OS?