When turned on, the system doesn't display on the screen. The screen is just displaying "No Signal". I checked the RAM Card (2GB) and seemed in good order, and the data cable is working well with other system but shows nothing on the particular Acer PC. The PC was working well until I tried to upgrade the RAM by adding another 2GB RAM card, now neither of them, when isolated, are showing anything on the screen.
Maybe you hit something when replacing the memory and now there is unplugged cable, or something else is not plugged in properly.
You can also reset the BIOS (CMOS). The pins you need to shorten usually are next to the battery. You also can google where those pins are using your PC model.