These files are indeed extremely important to any SharePoint deployment.  From time to time, though, someone gets the bright idea to tinker with them and break the site.  How?  Well, say someone decides to open up application.master in SharePoint Designer to make some changes for application pages.  Whoops – it’s dead.

Anyhow, since I have run into this situation more than once at client sites I figure that what is needed is a really easy place to get replacement default versions of each of these files so that you can go back to happily sharing and pointing.
If you need them, here are some download links.  Anyone without SharePoint will have no use for these files anyhow, and there’s no magic in them at all, but if someone at Microsoft has a problem with me linking to them feel free to let me know.
Happy SharePointing.