I often find I need to try this display on another PC and another display on this PC to sniff out where the problem is.
Hey, I have an HP Pavilion g7 with Windows 7 and I've recently been trying to extend my screen to an old LCD computer monitor I have using a VGA connection. I can connect it to the computer fine at first, but after about two or three seconds the external monitor goes dark. I can still faintly my background on the display, so I think the backlight just shut off, but it's not enough to actually see what's going on and I can't figure out how to get it back.
I frequently connect my computer to my TV with an HDMI cord, if that helps any.