ActiveState has not produced the .zip version for windows in a while. ActivePerl installs from .msi just fine & if it sees IIS is already installed, it will configure itself accordingly. Of course if you strongly prefer a copy of Perl as outdated as the OS you'd like to install it onto, you can always pony up for a Business or Enterprise Edition subscription.
Word to the wise: Server 2003 is under extended support for only another 2 years.