when i plug in hdmi cable to tv my computer screen goes black and i have to use the TV as the computer monitor, just happened

[ammcn]

computer problems
when i plug my computer via hdmi to a tv my computer screen (monitor) goes black but shows on the TV. i then have to use the keyboard but watch the tv instead of just looking at the laptop. this just happened yesterday and i am not sure why?

 

[CraigN]

The laptop seems to have been set to use the HDMI port as it's primary display when it's hooked up. Go into your graphic settings (Easiest is to Right Click on the Desktop and choose Screen resolution) and set it to Extend these displays instead. This will get you the use of both your monitors back. Click the one labeled as your laptop monitor and check the box for "Make this my main display".