WinXP it's like WinNT/2000 but more "smart" (too many stupid operations).
Firstly check what Apache installed for this to you need see all process runing <Ctrl >+<Alt>+<Del> Process.
If you see apache more than half of procedure to installing Apache+PHP done.
Firepages has a couple of suitable distros for XP, either phpdev5 (which bundles a GTK interface in with the *AMP setup) or phpdev423 (maybe with the php4.3 upgrade) which is very stable and straightforward.
I have never gotten PHPTriad to work successfully. My suggestion is to do a manual install on Apache, MySQL, and PHP. They are not that hard to install and you will be able to have the latest releases.