Problem with screen output to other devices

I have an XPS 17 (L702X) I was trying to do a presentation yesterday. I plugged in the adapter I purchased to go out to VGA, DVI, and some other plug. I plugged it into the Mini-DisplayPort connector and hooked it to the VGA plug. I turned on the F1 menu and chose the extend option. My screen came up on the other screen, but then it started blinking on and off the other screen. I wound up having to use another computer to do my presentation. I had just loaned the adapter to a friend with a mack book and it worked fine for him. Yesterday I connected an HDMI cable to my computer and shared my screen to my smart tv. I could get all the sharing options to work but the "second screen only."