Did that - nothing, what's more I couldn't switch the computer off iether by the reset button or Ctrl, Alt, Del. had to switch off at the mains, it maybe that it isn't starting up at all and not having anything to show on screen??? I don't know.
I had the same problem and I couldnt work out why it didnt work.
My comp would work for a bit then sort of go into a stan by mode. i couldnt restart it until I left it for a while. All the parts worked as far as i could tell so i let the 'experts' at pc world have a look. £50 later they told me there wasnt enough thermal grease between the processor and heatsink.
so rather than paying out £50 i suggest u get some thermal grease first.