@ DavidR,
I didn't know it was integrated into Avast itself; I thought it was a separate ".exe" that was invoked when the update was complete. Everything works fine, though, just wanted the old popup window back.
@ Staticguy,
I did try 2014, but I had waaay too many issues with it that I've seen others have had with it also.
Anyway, thanks, guys, for letting me know I can't change the update popup screen.