Okaaaay, here we go.
Go down the bottom right of your screen and hover over your battery meter.
Click it once and go into 'more power options'
The screen should say 'select a power plan'
On the plan which is selected, select 'change plan settings'
When the settings come up, at the bottom, above save changes and below the brightness settings, it will say 'changed advanced power settings,' click that.
Some settings should come up, and there'll probably be a scroll bar on the side, scroll to the bottom.
Expand the 'processor power management' section
Expand the 'System cooling policy'
Change both on battery and plugged in to 'Active.'
Shrink the processor power management and ensure you are at the bottom of the scroll bar still. There may be an option which says 'ATI Graphics Power Settings.' If you have this, expand it.
Expand any menus that come up, most probably about 'powerplay.' Change the settings on battery and plugged in to 'Maximize Performance'
Hopefully this should improve your situation.