Black/Multicoloured Screen

Right, I need all your help please.

Recently i've been expieriencing this "Multicoloured screen" sometimes after starting up my computer, or minimizing a game. I know its very unclear but I don't know how else to explain it. It may be a well known problem so maybe someone may know. I'll try posting a screenshot of it next time it happens.

 

Ok now i'm thinking its my monitor, I loaded up a game then minimized it as to get the 'multicoloured screen' so that I can get a screenshot of it. I pressed Print Screen and pasted in paint, but to my surprise the screenshot just showed the screen I took but normal (i.e not multicoloured) :S :S. Maybe my monitors dodgy?

Any help please.

 

The monitor is a CRT, right?
I had the same problem way back and it was the monitor. One of the pins was bent and then it broke off.
End of monitor.
Check the pins, make sure it is connected well and if you can, try another monitor to see if you get the same problem.
From the sounds of it, you can color the monitor 'gone'.