I built my own computer with windows vista a couple years ago then i upgraded to windows 7 when it came out then about a year ago my computer screen randomly flashes on and off. It usually does it when im using the computer a lot, like sound processing and video editing. My computer makes the sound like when something is plugged into a usb drive when it flashes off and then on. I have the onboard graphics card its like intel g33/g31 express chipset family. How can i fix it so it doesn't flash off and on and make the annoying sound?