I've recently purchased the Toshiba Satellite L650D-11R with HD5650 GPU. Unfortunately I can't update the driver via the AMD's site and the drivers provided by Tosh is seriously outdated,
Steam has an auto-update feature for ATI video drivers. Also, did you try going directly to the Catalyst page, or did you try the search function at ATI.com?
I used the usual drop-down system, which provides a link to download Catalyst Software Suite. The app only weighs ~1.1MB and it checks the GPU for compatibility prior to the actual download.
It seems certain manufactures do not allow generic drives from ATI/AMD and are very slow to provide the official drivers themselves. If that is the case, then I assume very little has changed since 2002 as I had identical issue back then,