You're not being rude (at least not to me). Don't know why I didn't google for those extensions
As far as I can tell, an XLK file is created by Excel 2000 and is some kind of a backup file. I got that from the FileXt.com website. I only have one XLK file in my system, but around 100 or so Excel 2000 files, so I'm not sure I really understand XLK files.
Maybe if I used Styles in my Excel files I would have more XLK files...
OTOH I have zero XLW files. FileX says they are for Excel 4.