Make sure all of your cables are good and connected securely. Try another OD. Unplug the OD when trying flash stick install. Iis this a known-good flash installer? If not write ISO again using Universal USB Installer
with Windows 7 in dropdown.
You'll need to get the disk booting, either by entering BIOS setup to set DVD drive first in boot order, tapping the BIOS one-time Boot Menu key at boot to select DVD drive, or autostarting PW CD to wipe the HD which will in turn cause Windows 7 DVD to autostart.
Are you getting the Press Any Key to Boot DVD prompt?
If these fail after trying them repeatedly - often disk is just being booted wrong - then test your HD using maker's HD Diagnostic extended CD scan.
This disk will also autostart and can wipe the HD after checking and fixing HD if necessary.