I have a work desktop, a Dell Vostro, which initially worked fine except for long periods of freezing after being awoken from sleep.
I consulted and was told it was a hard disk issue. I received a used 2.5" hard disk which I replaced the problematic 3.5" hard drive with, formatted and installed Windows 10 20H2, which I then downgraded to 1909 via a clean install bearing sudden blackouts and starting over multiple times.
I then transferred the old files from the 3.5" hard disk by swapping the 2.5" hard disk and copying it to a shared folder.
Upon removing the 3.5" and reinserting the 2.5", the machine could no longer boot, just a black screen, no Dell logo is seen, nothing. The fans are running though.
I have tried swapping it on a number of computers, disk checks on other computers, repairing the drives and nothing has worked. The 3.5" also no longer works and similarly can't be booted from. I am at a loss here.
Edit: I formatted my 2.5" and want to install Windows on it but I am unable to boot from my bootable drive (black screen). I want to boot from the 3.5".