Believe it or not, problem is solved. Read countless threads - most not helpful, tried a few, nothing worked. Finally executed hard shutdown; rebooted in safe mode. Held down Fn-F8 for several seconds - DISPLAY RETURNED! Opted to restart in normal mode as installation could not continue in safe mode. Again, Fn-F8 worked - and I completed my installation.  So … why did I lose my display in the first place? - and why was Fn-F8 useless as I tried for hours to figure this out?  Still don't know.  But thankful indeed for the opportunity to air this here.  Thanks, Mary G - for letting me know that there are caring folks out there. 
I NEED A HERO!   What alternative is there to Fn-F8 to toggle the video to an external display?  I have an external display connected to my E1705 laptop because my laptop display died several years ago (light tunnel problems).  No problem all this time -  a simple Fn-F8 would mirror the video to that external display.  During final installation stage of Windows 7, I lost my external display.  Fn-F8 does not work anymore, although it worked previously during the installation process when the boot disk needed to restart my computer twice.  So now, it's waiting for my input, I can't see a thing, and my heart is sinking to think that in this limbo state between a not-quite-installed Windows 7 and an old Windows XP that's been wiped out, that it no longer has the capacity to understand Fn-F8.    Am I doomed?  Funny, my machine DOES still recognize a WiFi toggle (Fn-F2).  How can I get my display back? - is there an alternative sequence?  Many thanks to any potential heroes out there.
HERO NEEDED: Lost my display DURING final installation stages of Windows 7