computer monitor keeps changing to a low resolution unexpectedly?

I have been having this problem for a while now where my computer monitor would unexpectedly go from the screen to a blank black screen and then flash back to normal or it would just change to a very low resolution and everything would look screwed up from the mouse pointer to the icons. Now I know it is not my monitor because I have replaced the old CRT monitor I had with a brand new LCD monitor just a few days ago and it is still doing this same thing. Also it can't be a virus because I have formatted and factory restored my computer about 5 times so far and that didn't do anything besides make me have to reinstall everything back on it. This problem just started a few weeks ago and after looking into it I have come to a thought that it is the video card that is going bad so i was wanting to put a new one in but i am not completely sure this is my real problem. I have an eMachines T6003, just in case you would need to know what computer it is.