Hi, I bought a refurb Optiplex 780 tower with  P2317HF Monitor a few years ago for my daughter for schoolwork. 

Today it's showing a 'No VGA Signal' on the monitor. We are using a VGA cable. I've switched cable ends, turned it off at the wall, etc, all the basic troubleshooting but it hasn't worked. 

I looked at some troubleshooting tips on here but they are not for the same tower and it mentions opening the lid and I'm not sure what that means, as I'm more of a basic user.

We can't go out to get cables obviously, but my computer (not dell) has VGA anyway. I think one of my sons has HDMI in his. She uses the computer to access her online schoolwork whilst we are all at home.

Thanks,

A mum!