It works! I re-installed everything from scratch (this time with Apache3.1.14/PHP4.03p1 cgi)! And - zoingg - all of a sudden that thing works! I get all my php-files parsed. I do not know what I did wrong with my last installation - I checked my configuration files and they are exactly like the ones I backed up the last time ...
never mind, on with the show!
If anybody wants to know how I did it
(Win NT 4.0 SP6/Apache3.1.14/php4.03p1)
drop me a mail and I'll send you my php.ini&httpd.conf files) ...