Screen goes black constantly

Alright, so I've had my PC for about 10 months now and I've had zero issues with it until now. Here's my build:

AMD Phenom(tm) II X3 720 Processor at 2.8 MHz
XFX ATI Radeon HD 4870 1GB VRAM
4 GB RAM
750 W Corsair PSU
Windows 7 64 bit

Now all of a sudden my computer screen will go black and I'm forced to restart my computer and the problem is getting worse and worse. It first started while I was playing Mass Effect 2, after about 9 hours of playing the game my screen went black and I heard a loud screeching noise from my speakers. I assumed it was just a random crash but it continued to happen whenever I played the game at random. Sometimes I could play an hour without it happening and sometimes as soon as I loaded the game I would crash.

Then, a couple days later I was playing a different game, Heroes of Newerth, when my computer did the same exact thing. This was odd, because I have been playing this game for a very long time and it has never happened before. It would continue to do this at random, sometimes I would have to restart every 10 minutes and sometimes I could play an hour before I had to restart. Then, that same day my computer screen went black while only browsing the internet. Now it has gotten to the point where anytime I load a game my screen instantly goes black and I have to restart my computer multiple times just to get my computer to start correctly. Sometimes my computer screen wont show anything until I've restarted it 10+ times.

Basically, here's the symptoms of what happens when my screen goes black:

-90% of the time screen instantly turns black, monitor power button turns from blue to orange as if the computer is in sleep mode, says no image is available. I'm also greeted by a loud screeching noise from the speakers.

-Occasionally while playing a game, the screen would slowly turn black and I could still hear sound for a short time before I had to restart.

-One time while browsing the web my screen instantly turned a gray color with the same screeching noise one time and another time with no noise.

-It usually takes me 10+ times to restart my computer successfully and get an image to appear on my monitor. Occasionally when I restart the words on the screen are jagged and impossible to read. When this happens after the boot up screen I get a blue screen with words on it but I cannot read them and then my screen goes black again.

-Whenever this happens and I try to restart my computer unsuccessfully, my mouse does not light up and my keyboard does not light up whenever I press capslock or something. However, whenever my screen goes blank my computer always remains on.

-Also, occasionally after my screen goes blank my fans get really loud, as if they are blowing at 10x their normal power until I press restart.

At first I thought the problem was Mass Effect 2 related because the problems coincided with playing that game so I used their support forums but as it continued I have been unable to pinpoint the problem. I have tried uninstalling and reinstalling the game, updating my graphics card drivers, dusting the inside of my computer, monitoring computer temperatures, and contacting XFX support. They told me to do a clean install of my graphics card drivers which I did and it did not work. While running games my CPU runs at about 29 C per each of the 3 cores and my GPU runs around 63 C and I'm not sure if this is an overheating problem.

I've gotten many responses, ranging from I have a faulty power supply, to my graphics card is dying, to my graphics card is overheating, to I have a corrupt installation of ME2, and so on but as of now, nothing I have done is fixed the problem as it has continued to get worse. What do I do?

what psu?
what are your specs?
download speedfan or coretemp to check temps and then report them here.
open up your case, and blow out all the dust with some compressed air. most important spots include inside the grfx card heatsink (may have to remove card), and cpu heatsink/fan. sounds.

If your having symptoms occur at system boot up, your problem is definitely hardware related or the way that hardware is configured in your bios.

What your stating points towards a video card related issue BUT that doesnt mean it couldnt be a ram issue also.

Is the system overclocked? If so reset your bios to default and double check that your ram speed and latencys are being set correctly by the board.
Test the system

Step 2. Remove and reseat the video card. Sounds stupid but ive seen it work before especially in cases of no display output at power on.

Step3. Switch the video card with another card and test.

step4. Remove one of your ram sticks and test in single channel. Then remove that stick and test with your other stick. Memtest is not a foolproof test, ive seen memtest pass memory that was most definitely faulty.

One of these steps should remove the issue, going by what youve stated in the way of symptoms.

If not you are left with your mobo next followed by your psu.

Your cpu wont generally give you issues UNLESS you have been running high vcore through an overclock and electrostatic migration has set in on your chip.

Hope this helps with your issue.

Well I tried switching my monitor to my second display port of my gpu and I actually was able to load a game today, but that doesn't mean much cuz I could still lose my screen image. If it happens again I'll try the other suggestions. Btw, my system is not overclocked and I am using the latest ATI drivers.

Well after 2 hours of working fine my computer went back to its same old state of turning black/blue/etc. I opened my case up and ran my computer and noticed that whenever I play a game a buzzing noise comes from my computer (not sure if from the mobo or the graphics card) and it persists until I close the game.

My motherboard is a ASUS M4A785TD-V EVO AM3 AMD 785G HDMI ATX AMD Motherboard. Unfortunately, I am a huge moron when it comes to computers (my friend put my current computer together) and I don't really feel comfortable moving all the parts around.

Sorry you posted while I was writing above, you have a definite issue if your computers buzzing mate!

If you have integrated graphics on your motherboard ( identifiable by a monitor output on the back of your case/mobo) Remove the video card and test with integrated graphics, see if your noise goes away. If you dont have integrated graphics you will need to swap the card out with a spare or a mates card and test. This should be your first step.

To be honest theres a 80% likeliehood that you have a dyeing videocard going by what your stating.

You board does have igp onboard I just checked. You can use this to diagnose your video card without pulling anything to bits.

Lol, thats twice in 5 minutes simultaneous posting, oh well great minds think alike so they say.

you can play it, at 4 whole frames a second!

Alright, thanks for your help all. XFX wants me to try the card in another computer before I can get an RMA so I will do that and call them back tomorrow.

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