Actually, it would be more accurate to say that they stopped supporting Win98 a little over a decade ago, but ...

If you insert your Word (or Office) installation disk, it should open the "Installation Wizard" automatically. If it doesn't you can look on the install disk (or first floppy if it's really old) for a "setup.exe" file or something similar and double-click it.

You should also be able to go into Control Panel and double click on Add/Remove Programs (or something similar) and click on Word, then follow instructions. You may or may not need the Word/Office installation disk when you do it through Control Panel, depending on whether the installation .CAB files are on your drive.

The usual instructions about backing up before making changes apply, of course, but installing Word shouldn't overwrite or remove any .doc files. It may give you a new normal.dot, which is the "empty document" template that opens for new documents, and that contains all your macros, styles, etc - assuming you've created any. If there's any question, you can search for *.dot and copy any that you find somewhere else before you do the reinstall of Word.

If there are any problems with the installation, you might need to use Control Panel to uninstall Word¹ and then use the installation disks to re-install it. A little more care with backup of your .doc files before doing the uninstall step might be in order, if any of them are in the program folder(s).

¹ In some cases of incredibly profound corruption, the last resort is to install a program so that you'll be able to uninstall it (using Control Panel), after which you can get a clean install; but I've never heard of this bad a situation with Word or other Office programs.

John