IISAdmin.Net を使えば、WindowsXPでも複数のサイトが保持できます。

おっとお。気になるのでメモ。

If you're working on more than one site at any given time, you are forced to "manually" switch the IIS from one site to the other using the IIS MMC. IISAdmin.Net semi-automates this process by maintaining several configurations side by side and switching between them (using ADSI) with a single click.

IIsAdmin.NET: Create Multiple Web Sites Under Windows XP
By Mark (Code6) Belles, Gabe Wishnie