BadBlue's new Personal Edition has been tuned for XP Home. XP Home, of course, doesn't include any sort of web server. BadBlue is a freely downloadable web server that is a tiny download (just a little over 500K).

There is a wizard and illustrated tutorial for setting up PHP.

Free download of server -

Installing PHP and a server on your Windows PC -

Writing your first PHP script -

Very easy to setup and it's so small you can carry it around on a floppy.