accidently overwrote index.php

I am using WordPress Default 1.6 by Michael Heilemann and accidentally overwrote the main index.php with another php file.

Now I can’t access the main page. Instead I get a fatal error message (because it’s not the right file anymore).

Is there anyway I can overwrite it again with the correct index.php and, if so, where might I find that original version?

thx in advance …. “the dunce”