Are any other appliances in your house having problems or is it just the computer?
Try unplugging, one of the appliances in your house, that you know is working, and plugging the computer into that plug......If you don't have a multimeter to test the outlets you are working with, its probably best to just borrow an outlet from a known working appliance or other electrical device.
The next thing I would try after that, is to unplug the computer, open it up and remove the CMOS battery (shiny round thing that looks like a nickel) for a minute or two, reinstall it and try powering on your computer again...........
I'm out of Ideas now, anyone else?