Envy17 screen flickering when AC plugged in

So, I've had this laptop for about a year now, it wasn't newly bought I got it as a gift from my dad who in turn bought it from a friend. Now, throughout my ownership of this laptop, the screen would occasionally flicker whenever I moved rooms but that would be remedied by simply unplugging it from the laptop and plugging it back in (Also, this only started happening when the initial charger I got with this laptop stopped functioning and I got a new one) In addition to that, about 4 months ago I lightly dropped it while it was on and the hard drive fried, ever since that whenever the screen is tilted or if light pressure is applied to the back.
Now onto the problem at hand. 2 days ago in the morning my father asked to borrow my charger since his recently broke, so in my drowsiness when I gave it to him I dropped it. When I came home from school that day and plugged it in the screen started to flicker a bit at the top and it only does it when I'm doing something (such as watching a video or opening a program like a video game, in addition it goes extra flickery whenever its on full screen) This flickering isn't like a brightness flickering where it goes from bright to dim as if someone is unplugging and plugging it back in over and over again really fast, its more like the top of the screen goes up and down erratically with random lines visible.
So after all this I snooped around and tried to fix it myself by first checking for new updates to drivers; everything was up to date. Then I uninstalled my drivers and upon restart windows automatically installed what I'm assuming are just basic VGA drivers and with these drivers the laptop would never flicker. I thought to myself that maybe my problem was fixed so I updated to my old ATI drivers and upon restarting for the changes the flickering returned and again it was only while the charger was plugged in and had a power supply. I tried having the charger plugged into the laptop but not in an outlet and the flickering is absent... My guess is that its the charger but I have no idea and I'm a very cheap guy so I'm relunctant to buy anything without knowing it will work, or at least have strong assurance from people who know what they're talking about.

Thanks for your time~