Your new video card's refresh rate is incompatible with your monitor. Follow these steps to fix it:
1. Restart the computer, and while it is restarting, press F8 until the Startup menu appears. Press 3, and then press ENTER to start the computer in Safe mode.
2. Right-click the desktop, click Properties, and then click Settings.
3. Click Advanced, click Adapter, and then click Adapter Default from the Refresh Rate list.
4. Click OK, click OK again, and then click Yes to restart the computer in Normal mode.