RE: Just "installed" Radeon R7 250 graphics card on my Dell Optiplex 9020. Black screen when I plug the monitor into the card. Help!
Did you upgrade the power supply unit? Adding a separate card automatically disables the on board graphics. However most Optiplex computers are low powered and need power upgrades to run today's video cards. Yours has less than 300w psu and that can't run high powered cards.