But seriously.. Turn on the computer, see what appears or doesn't appear on the screen. If you see something like "Press F2 to enter setup" and "Press F12 for boot options" (shows just for a second or 2), then all is not lost. Your message may be different, or a colorful message screen shows up, that's good too. Poke the F6 key once a second as it is starting, do this for at least 10 seconds and see if a black & white boot choices menu screen appears. If you get no response whatsoever, try a different monitor, or check all connections to your monitor.
A setting in your BIOS may be wrong as a result of a dying battery also. Some mainboard BIOS systems will automatic revert to a failsafe mode if the power is turned on and then off in a second or 2 without allowing the POST to complete.