Overclocked with Rivatuner, screen stays black?

[gumdrops]

I'm a noob to overclocking but I thought I'd give it a try and went into Rivatuner and click the "Detect Now" button which set my clock speeds automatically. I selected load profile at startup then restarted, but whenever Windows finishes loading, the screen stays completely black. How do I go about reversing this action?

This is persisting even after uninstalling Rivatuner in Safe Mode.