You may want to experiment and see what line in those files was causing the problem. Edit them, e.g….
And put a rem in front of one line at a time, e.g.,…
Rem <rest of the line>
(note the space after rem)
And save to…
Or, the problem could have been caused by a recent software install. Most of these installs will back-up the configuration files before modifying them. Search for the backups with…
The * can be .bak, .tmp, whatever (I use .dux because no one else does and future install programs will not overwrite them). Looking at the dates will indicate which is the most recent. Try renaming them to .bat and .sys, respectively, after making sure you have a backup of your originals.
Windows 98 does not need autoexec.bat or config.sys files (Windows 95 does), but some older devices and programs may need them.