how did you install your graphics driver? with laptop GPU's its really best to avoid the drivers from AMD's website and use the ones from Acer's website, even if they are ANCIENT.
this is because the Acer drivers are better able to handle the power management settings of the laptop that AMD drivers weren't meant to do.
Well, why would that matter? you say
if the graphics chip is thinking its supposed to be a 'low power' state, it won't clock up to perform at the level it should during gaming, therefore placing more burden on the CPU that it was before you formatted
so check your power management features and make sure they are working correctly as well
also, you might double check the graphics settings, if something like 'post process' or AA or something that gives higher detail was accidentally left on..., that can cause chugging