That's because the USA Benq website is down. I don't know if this is a temporary or permanent condition but you can click on the link below and select another country and probably find the driver. The post of mine above was posted over a year ago so it's possible the link has change but no link will work on the US website at the time of this post.
Code:
http://www.benq.com/support/
or
Code:
http://www.benq.co.in/support/downloads/index.cfm?productline=9