I already have a notebook with GMA 4500MHD and in a similar problem as you intend to be.
I bought a VGA to S-Video/RCA cable from Amazon but it does not seem to be working.
Please see my post and reply if you have found a solution.
I have two lop tops wiht the 4500MHD and bought the same thing on Amazon....I have spent 3 days trying to do research and get it to work....
Could you please advice how did you get it working, i have bought the same adapter but it does not work on my Toshiba Tecra R10 with 4500MHD on board.