2310t sleeping

I have the HP2310t monitor,the problem is that after about 15 minutes the screen goes black,like a screen saver and I need to move the mouse to get the screen back.

How can i disable this,its annoying because it stops me watching movies.

I know its the monitor and not the computer because when I use another monitor this does not happen,it only happens when I use the 2310t.

thanks