Whenever I boot up my computer the screen will turn on for a second, then go black, but the power light stays on. While it goes through the BIOS screens, Window screens, etc...it will keep flashing on every time it reaches a new screen, but instantly goes black again. It also makes a very slight beeping sound coming from the back of it. I tried shining a flashlight to see a dull image, but I don't see anything. What could this be, and is it worth replacing or just buying a new monitor? Thanks!