When I try to boot up my Gateway GT5670 pc the Acer monitor says no signal. I think it coud be the power supply. This computer is 4 yrs. old and I've replaced the Motherboard, Video card, hard drive, cd rom. About all I have left to replace is the fan and power supply! :>) Are power supplies compatable or do I go by the name of my pc? I'm not real savvy when it comes to a pc. All I know about this one is that it says 300.0 watt. Is that what I need or can I go higher on the wattage? Thanks in advance.