Dell blank / black screen

Hi everyone,

I have a Dell Latitude E5430

I logged into my computer this morning and as I had it connected to a projector yesterday the screen resolution was not correct. I got a message stating this so I decided to change it in settings. I right clicked on the desktop and instead of going into properties I noticed another selection. I cant remember what it was but it was to do with displays. I hovered over the arrow and there were a few options, the third one was clone display or similar but again I cant remember what the others were. I accidentally clicked on one of these and the screen went blank. The computer was on and I waited a few minutes as usually once display settings are changed if you don't click yes it goes back. Needless to say it didn't. I restarted the computer and after the windows start screen it went blank again. So far I have tried;

1. Connecting to a monitor via HDMI Cable
2. Connecting to a monitor with a VGA cable
3. Going into safe mode and changing resolution
4. Removing the battery and holding down the power button for 60 seconds then turning back on

The first two just left a blank screen on the monitor and the 3rd and 4th made no difference once started in normal mode. Other posts mention pressing F8 but this doesn't do anything for my computer.

Any help will be much appreciated and thanks in advanced