Test your hardware with the self-booting CD's in the Troubleshooting tutorial note at top.
Reset your CMOS to try to get a disk to boot: Clear CMOS - 3 Ways to Clear the CMOS - Reset BIOS
. Try writing installer to flash stick to eliminate possibly defective DVD drive, using Steps 1 and 2 of tutorial in blue link two paragraphs below. If flash stick won't boot, unplug DVD drive to try it again. Try another DVD drive.
If media will boot proceed with troubleshooting steps to disinfect, repair OS and boot, rescue files, if necessary reinstall or recover.
If not rescue files using Paragon Rescue which boots itself, try booting DBAN or Partition Wizard
CD which should also boot itself to wipe the HD, which in turn should allow installer to autostart to Clean Reinstall - Factory OEM Windows 7
This will solve an issue where boot code is blocking boot of the HD, disks, and sometimes BIOS POST. It must be wiped with the equivalent of Diskpart Clean Command
, even if you have to move HD to another machine.
However if a failing mobo or other hardware anomaly, this may not be enough.