Parsing HTML Error

Here's a weird problem. - Using IIS on Win2K w/SP1 - Setting IIS to parse .html files with PHP.exe, same settings as for .php files - NOT using ISAPI module HTML files are parsed properly and php code is executed for the following browsers. All versions of IE on the PC IE 5.1.4 on MAC NS 6.x NS 4.78 (as part of Communicator) However, for NS 4.72 (as part of Communicator) and for IE 5.0 on the Mac the HTML is not parsed and the PHP code is not executed or removed from the html. I wouldn't expect browser or OS versions would have any effect on what the server parses or not. Any ideas? Thanks. Ivan