Need help with computer screen going black?

I have an inspiron 2305 all-in-one and lately the screen would turn black and have to forced to close.

I have been unable to even find a pattern to when it happens, the screen will just turn freeze for a bit and then turn black. I do play games like dota2 and lol on the computer but it seems to happen just as much when I am not playing. When it goes black I am usually able to hear it making a buzzing noise that will sometimes be faint and sometimes loud varying for one occurrence to another. The computer after I left it at log in for a while. After some research I thought it might have something to do with overheating but since then I have dusted out the computer and have been using SpeedFan and this has not solved the issue though the computer isn't getting as hot which is a step forward :/