Hey. Is the md5 sum (a2dc5ffbeddef7c67b1ac9c1a4a3b408) listed for php-5.1.0-Win32.zip accurate?
All of the mirrors I have downloaded it from give me 93152588795d377743fe1b1fb1680b84.
Here is the main PHP download page: http://www.php.net/downloads.php
I get 93152588795d377743fe1b1fb1680b84 too, and that's listed in php.net downloads page. Could have been corrected after your post.
Looks like it has been fixed.