Are you running this server yourself, or is it an ISP?
There is a way to get the server to parse include files without having 's' in the suffix, but, according to my IT folks, a number of things can go bad (M$ lives!) - including asp, indexing, certain bots in FP, etc.
I'm not running IIS, so I don't have an exact answer, but basically right-click on My Computer, Properties, find the server tab, click on the root level icon, and "somewhere in there" is a tab that will allow you to make the addition. Not much help, I know, but best I can do off the top of a few heads.
Bottom line - Apache...
