Which Windows?

You can go to the Control Panel and find the Power options. You can change the amount of time it takes for the display to turn off, and change when/if the computer goes to sleep.

- right click desktop
– properties
– screen saver tab
– power button
– change monitor and hard drive turn off to the desired time period

Go to control panel and then power. You can set the time for your computer to be idle before it goes to sleep.

I downloaded this application called caffeine. When turned on, it stops your computer from going to sleep mode/black screen. I use it when watching movies.

I’ve noticed something that might help you. When I start my computer (this is with windows xp), it goes to the login screen, where I choose the particular account I want to access. If I click on the account within a relatively short amount of time after it loads, I have no problems with the sleep mode, it works just fine. However, let’s say I turn on my comp, but I go run and do something else for a few minutes. If I let that login screen idle for more than 10–15 minutes, the computer goes in and out of sleep mode, no matter what I do in the control panel. I don’t know if yours does the same thing, but maybe that can be of some help to you.

@mrentropy Thanks it worked :)

@Chikipi Good :) My next step was to say try pouring coffee in it.
But don’t do that.