Tried them all--should have included that. F12, F2, F8, etc.
It's obvious that the bios command isn't being recognized--the question is why? The USB keyboard input IS recognized during non-standard startups (i.e. following a crash) when the DOS type screen is displayed asking if I want to enter safe mode, normal start, etc.
My next step is similar that that listed below--but since the computer has no PS/2 or serial type inputs I must first buy an adapter.
OS is Windows 7 and is fully updated as are other peripherals, etc. via Dell's support page.