Slow in what way? Is it just the UI responsiveness or the whole system? Did you install all the drivers for your hardware? Go to device manager and check for any issues..
A gpu generally won't slow down overall performance of your pc like that, maybe it's another component that is causing problems. First update the drivers to the Crimson suite, if that doesn't fix things check if you're facing the same issues by running off onboard graphics or on another gpu if you can borrow from a friend. If the issue still persists run HD tune and memtest to check other components.
Slow in what way? Is it just the UI responsiveness or the whole system? Did you install all the drivers for your hardware? Go to device manager and check for any issues..