I_Brian - 9:15 pm on Nov 18, 2004 (gmt 0)

It's possibly better advised to circumvent the issue of filt type in the first place, by concentrating your URLs into folder paths, ie:

example.com/keyworded/folder/path/

That way, if your site development changes and you're requirement to change file types, it won't be an issue and the change would not affect established rankings for those folder URLs.