I had the same problem with the same motherboard: it said press F2 for bios options or press F10 for boot menu, but the system was unresponsive to either key.
I turned it off and on a bunch of times to no avail, reset the cmos, and gave up. Then there was unplugging and replugging of the wires, followed by a successful boot. I suspect this may be a case of the power supply being insufficient to complete the bootup process, but I have little evidence with which to support a conclusion of causation. My advice is to avoid rebooting your computer unless you have no other choice once you get it to turn on.
Computer in question is an emachines c3070.