Microsoft's Web PI is a comprehensive package assembled by Microsoft to enable an easy build of their web platform. The package includes Internet Information Services (IIS), SQL Server Express, .NET Framework, Visual Web Developer Easy, Silverlight and PHP.
Version 3 (7/2010) and Version 4 (10/2012) are mature and well tested by the developer comunity, ensuring reliability. There is also an automated Web Application Gallery, allowing for easy installation of 3rd party software such as WordPress, Umbraco, Drupal and Joomla!
Web PI is free.
Setup is more tedious than XAMPP, but the instructions are clear - you just need more patience.
It can be downloaded from http://www.microsoft.com/web/downloads/platform.aspx, where there are links to just about everything you will need to know. There is also an active forum, if you need help.