Is this a new build, or has it suddenly stopped working?
What exactly is it? Intel, AMD, what? details always help.
usually a good step in these situations is to try removing everything apart from the CPU (& its HS of course), the gfx card, and a stick of RAM - that's all you need to get to the BIOS.
If you do that and it still doesn't work, try removing the mobo from the case and putting it on a non-conductive surface and again just running with the gfx, CPU & some RAM.
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<font color=red>Those of you who think you know everything are annoying to those of us who do.</font color=red>