Monitor issues

I would like to start off by saying I know that this is the wrong place to put this but, I've tried putting it where it belongs but I haven't gotten a reply, and I need one as soon as possible.

My monitor keeps getting a black screen right when I turn on my computer, basically when I turn it on I see windows start up for half a second then i get the black screen while my monitor is still on

Now I just recently built a computer, put it all together a couple days ago, the same thing happens, I haven't installed anything not even windows 7 yet, but when I turn on the computer I get the black screen again I can't install windows

My brother and his friend think its the graphics card, but when I built my new computer the black screen continued to happen. If i turn off and on my monitor I get to see my screen for half a second then it just goes black again.

Yes I did check the cables for the monitor, I even plugged it into my laptop and the same thing happened to the monitor

So I was wondering.. what is causing the problem? my brother thinks theres something wrong with the new parts i've bought, I think that its the monitor thats causing the black screen.. which one is it?!

sorry if this is all over the place or doesn't really make sense, was in a rush in writing this.