I finally got the following set up on my (ack, cough) Windows XP machine:
Apache 2.0.49
PHP 5.0.0RC3
MySQL 4.1.2-alpha-nt (using MySQLi)
phpMyAdmin 2.6.0-alpha2
I know a lot of people have trouble installing a setup like this, so here are a few notes:
If possible, start from scratch. Uninstall MySQL, PHP, Apache. I had a much easier time this way.
Set extension_dir to the proper path for your extentions in php.ini. For me, it was "C:\PHP\ext\". Make sure you include the final backslash, although on my system it didn't seem to matter. Most people recommended it.
uncomment the line "extension=php_mysqli.dll" in php.ini, if using MySQLi, and "extension=php_mysql.dll" if using MySQL.
copy php5ts.dll to your Windows %SYSTEM% directory (for me, that was c:\windows\system32).
copy libmysqli.dll (if using MySQLi) and/or libmysql.dll (if using MySQL) to the Windows %SYSTEM% directory.
I missed copying the dll files to the system directory. I kept getting an error trying to load phpmyadmin, "could not load module," failing on php_mysql.dll. That was confusing, and I mucked with the extension_dir for hours. I finally went to www.dependencywalker.com and downloaded a very cool app called Dependency Walker. I ran it on php_mysqli.dll, and discovered that it couldn't find the libmysqli.dll and php5ts.dll files. Strangely enough, even though all of the "php_" extensions are in the ext folder, those two (and a few others) are in the root PHP directory. Copying them to the window system folder solved the problem.
I think that's most of the "gotcha's" of the installation. If I have missed anything, please use this thread to add it, so that other people trying to install this "uber-alpha" setup can do so without the toothaches I had to endure.
Thanks!