Win98 missing system files

A client of mine has a notebook running Windows 98 SE. Since about 3 days ago, every time when the system boots up, it complains that a device bi-di.386 is missing. The system.ini does contain the line “device=bi-di.386” in the [386Enh] section. After pressing any key, the system continues with the boot up.

This error happens without any changes to the computer.

Any one knows why this happen?

I believe I can comment out the line in the system.ini but I wish to find out why this happens before I do any thing else.