ACER 17" black monitor

first, I would check screen cable. try replacing it with a new one, you will be surprised to know how many display problems are are caused by a defected screen cable.
in case this is not the problem, it can get more complicated, but first, just in case, reinstall drivers. its a long shot, but if you get lucky it will save you alot of pain. in case it didn't help, It's probably a bad vertical output chip. if you have some familiarity with monitors and decent soldering skills you could probably fix it yourself, but I would advise looking into taking it to a shop, or at least find an experienced hobbiest if you're not yourself. It's a pretty straightforward fix for someone who knows what they're doing.

good luck.