My computer screen at times randomly goes completely black. about a week ago, my computer would just shut off randomly, found out it was the fan, it was a little out of place so it wasnt cooling the processor enough. Fixed that. Now the computer stays on, but the screen goes black. Its not the monitor, I tried replacing it, replugging it in, everything. I checked the video card, unless I just need a new one, its fine. In place and everything. I dont know what to do at this point. Sometimes it does it right away and sometimes it just waits awhile (like until im in the middle of something really important and am just about to hit send ) Please help.