This one is clear. It is still the ATI graphics driver
that crashed. This could be caused by driver incompatibility (if you did not succeed in fully de-installing old). Or due to a HW failure in your card.
Lets test the latter first. Take out your graphics card and use the onboard graphics?
Also... was this pc functioning correctly in this hardware configuration before you installed Windows 7? I've seen some reviews that seem to claim that your mobo cannot handle that cpu?? But if you've worked fine in the last three years that must be old or wrong info.
Looking through the dump there is one other possibility, a long shot but I've seen it before...:
The dump has had difficulty with some of Norton's drivers
. We have seen problems with Norton that appear as though it is HW or drivers.
As a test I would fully de-install Norton and temporarily use MSE or Avast!, both free.