Everything works fine for about 1 or 2 hours and then my monitor goes to sleep.Also,it seems that programs(video games and such)make the monitor to go sooner to sleep.I have to wait some time to turn it back on because when I turn my PC off and restart it the "monitor going to sleep" message pops up during setup.I've tried changing the sleep settings to never but it doesn't seem to work.

If it helps my monitor is a HP w2007v and PC HP Pavilion and using Windows Vista Black Editon 2009.Oh and my Pc's Model is :a6644sc

Have you tried another monitor? The problem may not be the monitor. The monitor going to sleep message can also occur when the monitor is not receiving a video signal from the computer. Check that the computer or video card is not overheating due to fan failure or dust buildup.