This
could be memory related based upon the symptoms. Download the latest release of Memtest86 from
here and make the floppy. Check the Readme, boot with the floppy* and run the checks. It can't hurt and will eliminate this element of the problem resolution.
* You may have to set your bios boot sequence to the floppy as the first boot device.
Once you've eliminated the memory factor, if you haven't already, you could also boot with a 98 EBD and run a thorough scandisk on C: from DOS. ie;
scandisk/surface c:
It'll take a while to run using the /surface switch. Check the memory first. If there is bad memory, it will cause disk errors, data loss or corruption, or both.