I have a dell desk top computer that is about 3-4 years old. Over the past 6 months I've had 4 different monitors stop working with this computer. Each time I go and get a new one (2 were gently used 2 were brand new) and every time it will work for about a month or so then I'll notice it'll flash on and off occassionally but just a quick flash then out of no where it won't turn on anymore. The green light will turn on but no picture. At first I thought it was the monitor but after the 4th monitor I'm starting to think it may be something else. Please help, I cannot afford to go through so many monitors!