This year I've decided to enter the EuroWinPHP contest, as I figured it might be interesting to learn a bit more about how PHP works on Windows.
I originally started using it there, back in around 2002, running early versions of Apache 1.3 and PHP 4.1 on Windows 98 and 2000.
These days, though, I'm running IIS7 and PHP 5.3.2, and have a bit more knowledge of how the bits fit together, though since I've been running Linux for the last 5 years I'm a little out of touch.