Just installed a new hard drive into an OptiPlex 9020 MT.  Followed Dell's install instructions after downloading the iso for Win 7 (UEFI boot from flash drive). When installing from a flash drive, Win7 installs and on reboot starts to install over again. This happens 3 times. I figure it's because I didn't pull the flash drive fast enough during a reboot cycle. I pull the flash drive and the system starts. The Dell logo is on the screen for all of about .25 seconds, then No Boot Device: Retry, Enter Setup, or Diagnostics. I retry and it works. Almost every time.  But it's always on retry, never on initial power on. Setup never shows. Just a black screen. I have gotten it to show once since installing Windows 7. Should I reinstall again under Legacy Bios? I've installed all the new drivers and the latest Bios (A23) that Dell has to offer for this machine.

Thanks in advance!