Start by running sysedit from the run box on the start menu.
Look in autoexec.bat, config.sys and the 2 windows system configuration files for any lines that attempt to load a DOS CD driver.
MSCDEX is a common DOS mode driver.
You ONLY need the DOS mode driver for DOS mode games that run off of a CD.
To test what you find, place the word rem and a space at the start of the line that calls for the CD driver.
If that does not fix the problem;
open device manager,
expand the CD drive branch,
select your CD drive(s),
right click and select remove.
After removing the CD drive, re-start Windows and see if Windows finds and loads the correct driver.
You may need to download and install the chip-set driver for the motherboard.
If it is a VIA chip-set, read the notes on the driver download page at www.viaarena.com
They have a legacy driver that many users have reported as being more stable for W98.
If the board has an Intel chip-set, you may still want to use a legacy driver rather than the latest.
What you want is the "Intel? Chipset Software Installation Utility".
If you choose the 810 chip-set and W98SE, you get to a list of drivers that support most of the PIII chip-sets.
Chas