I'm a member of a few forums, but this one seems the most appropriate for this particular problem.
First off, I purchased 3 decommissioned Dell towers from my wife work. I'll refer to these as towers A, B, & C.
All 3 are Intel Core2 Duo's w/ 4GB ram. I provided my own HDD's.
Tower A: Optiplex 780 w/ Win7 Pro COA key.
Tower B: Optiplex 780 w/ Win7 Pro COA Key.
Tower C: Optiplex 360 w/ WinVista Prem COA key.
Tower A: I installed Win7 using a factory OEM Win7 install disk. No problems and working great.
Tower B: I've tried 3 different Win7 install disks, including the same one used on Tower A: Every time it loads the setup files, and starts the install process. Every time, after it's first cycled reboot during install, it goes to the Win7 splash screen, then the screen goes blank afterward. I swapped the HDD from Tower A: over to Tower B: and it loads fine. So, I tried installing the OS for Tower B: using Tower A: and I get the same blank screen issue as if I were installing in on Tower B:. That led me to believe it was possibly the HDD. However, it will take a Win10 install no problem.
Tower C: Haven't touched this one yet. Waiting on a Win7 key to upgrade it because Vista has such a negative stigma.
Any geniuses out there with a viable solution to this problem? My OCD is causing me great stress with this one.