You haven't got a video card as well as onboard graphics have you? In any case, as hari says, try just a simple VGA monitor, something other than you are using right now. If you see the boot screen menu then unless you have multiple graphics chipsets you should see the rest until just before the AV Wizard. Although it is possible it could be a weird screen pickiness thing!
btw, don't both pressing the keys - that is for the AV Wizard at the end of the install after a reboot, 40 mins later. After the install option it asks you questions about which drive to install on ... it is just sitting there waiting for you to answer and not doing anything. Best not to press keys blind if you have any drives with valuable info on in that machine! No, it isn't rebooting, otherwise you would see the Power On Self Test BIOS screens etc each time.