Video card installation ( beginner )?

Hi this is my first ask so please bear with me. I have a Intel core i7 12 gb ram 64 bit processor computer. If i missed anything i can try to figure it out for y'all. A few weeks ago my monitor started flickering and then one day went out. Panic. Then once i was sane again i started to troubleshoot. I replaced the vga cable and it worked for a day and half. Went out again same black screen. So i got a new video card ( galaxy ge-force 620 from best buy, and installed it. Worked beautifully except it was beeping when it installed and when i turned the computer on ( Beeping: 6 times about a second or second-half ) then 2 days later ( yes i used it even though it was beeping. Played minecraft. And more research ) worked for about 2 days then the screen went out. The built in video card still works. But won't play minecraft ( big huge problem) so here in lies my question… What next. If anyone can help or offer advice i'm very thankful.
-Brittany

Beeping often indicates motherboard problems, although it could be a few things, the only way we will know is if you know what mobo you have…

Lets start with the beeps… Read here http://pcsupport.about.com/od/nonworkingcomponent/ht/beepcodestb.htm and post back what the error is and we can go to the next step.

Sounds like your motherboard. Also, I hope you didn't spend more than $25-30 for that GT 620 because its a HORRIBLE graphics card, and is barely better than integrated graphics. Its very weak.

And before you start adding switching graphics cards anyway, you need to make sure you have an adequate PSU. 450 watts or higher.

But the beep codes are indicative of a mobo problem, and you need to listen to how many, and then contact the mobo's manufacturer's website for info.