You had another graphics card installed before? Probably a driver conflict.
1) Remove your current graphics card and turn the computer on. Log into Windows.
2) Press Windows+R. Run opens. Type in cmd and press Enter. Command Prompt opens. Type in SET DEVMGR_SHOW_NONPRESENT_DEVICES=1 and press Enter.
3) Open Device Manager. Open the View menu across the top, select to show Hidden Devices. Find your old card in the Display Adapters category, uninstall it and say yes if it asks to uninstall drivers.
4) Shut down, insert your new card, boot your computer, download and install the new drivers.