My Acer x263w displays "No Signal" right in the middle of the screen, unmoving too, when my Win 7 x64 PC is asleep. It is connected to an ATI 5450 chipset video card via HDMI. I have 2 other monitors ...

Your friend is mistaken. This serial port he is talking about is called "CGA" and closely resembles a serial port. However it still requires a graphics card and a monitor! You can convert a CGA signal ...