Monitor Problem

I recently had my hard drive wipped and reformmated. The XP home version was reloaded on the computer. When I brought the computer home the monitor started to turn itself off for about five seconds at a time and changes the setting size periodically. The RAM is 256, I tried to find the further information about the computer but could not figure out where to find it. I checked the power cords, when the monitor shuts off the power is not shut off on the monitor. The monitor was made in 2001 and is a AOC model number 7Elr made by Envision Peripherals, Inc in CA. I went to their site and downloaded the driver, I put the OS disk back in to try and reinstall a driver from the hardware menu but neither of these solved the problem.

Can anyone help, please.

Thanks
LMC