Startup problem with reinstalled NVIDIA RIVA 1287ZX driver

This is my teenage daughter's existing machine with W98SE
and original video card and NVIDIA RIVA 128 driver where
all worked fine. KDS CRT display died and I replaced with
Sceptre V5G-Komodo-7 flat screen. Machine then went to
default VGA with unchangeable 640x480x16. Found correct
driver on my existing W98SE onboard files and loaded it--
Video-78 NVIDIA RIVA 128ZX ver 3.37. This cleared up the
resolution problem as expected and display works fine.
Removed some spyware and threw away an unidentified blank
folder on the desktop. Also updated NSW/NAV 2003 Pro.
Now machine (1) bypasses second BIOS startup screen (blank
screen displayed), (2) will hang up on attempt to go to
BIOS setup mode with DEL key, (3) will not respond to
existing W98SE startup disk, and (4) gives blank
screen/will not respond to F8 or Ctrl to go to Windows
Options mode (cannot get into SAFE mode or any of the
other options menu modes)/and goes directly to bkgrnd with
icons with no display of "W98SE" startup screen--once it's
there the applications seem to work fine. Can't find any
way to get it out of this mode. Any help would be
appreciated.