possible bug or ?

hi all, To this newsserver i'm new but i use php for over two years now.Last night i checked the offcial php website to see if ther is a newer version relased as mine 4.1.2 so i downloaded and installed the latest php.i edited my httpd.conf file and installed php as module restarted my apache server and by a test i tryed to submit the form on my website apache said "http 500 internal server error" usually this is related to the files rights read write etc CHMOD but i'm on windows 2000 so there is no CHMOD what is wrong here why do i get that error ? the same form worked fine with the php version already installed it always says that i created a little sscript (http authentication) to test when i run it > http 500 what is this ?? regards from belgium Erik