Dual monitor nightmare

Hey,

I plugged an old tv to my daughters computer (Dell inspiron (self contained comp in a screen) running windows 8) via a hdmi cord but couldn't get the computer to display on the tv (tv and cable are fine, it works great with my computer). I tried everything in the display settings and the last thing I tried which was a mistake is make the tv my primary and only display. Now the computer screen just glows and I can't get it to display anything. I was able to get into the set up utility by pressing F2 but that's it and there's nothing I can do there.

Your help will be greatly appreciated, I'm kind of going nuts here