Radeon Mobility HD 4570 Not Working

A few teething problems with Windows 7... I recently purchased an Acer Aspire 7535G with Vista - it has two graphics cores - an on-board 3200HD for low power stuff and a more powerful HD 4570. These are controlled by Catalyst Control Center (CCC) and worked fine...

...until I upgraded to Windows 7

- Now Power Express does not seem to recognize either cards although the 3200 appears to be working. When I check the hardware section of the computer, both cards are recognized, but a fault is diagnosed with the 4500 series card - it says the card cannot start - code 10 error

The cards are supposed to switch automatically when the computer is plugged into / out of mains power.

I have downloaded the most recent versions of CCC and the most recent ATI drivers but this has not rectified the problem.

I need the 4570 card. Has anyone experienced similar / suggest a solution??