You should use the sticky under this forum to do a clean driver install. You have to download a tool to remove your old graphics drivers and then do a clean install. The directions are posted in a sticky here, along with a link to the software. If the only thing you changed was the graphics card, I would be almost certain you're trying to use an obsolete driver along side the one you should be using. (Basically 2 drivers are trying to send information to your card and over driving it is my guess)