Microsoft WebMatrix is a free web development suite that aims to simplify the process of building professional, dynamic websites.
Installing WebMatrix will get you IIS Developer Express, an easy-to-use version of the IIS 7.5 web server that ships with Windows 7 and Windows Server 2008 R2. SQL Server Compact handles all your database needs, and you're able to code your site in ASP.NET.
You can add an array of Microsoft development tools to this list, just by checking a few boxes in the installer: PowerShell 2.0, Visual Web Developer 2010 Express, Windows Azure tools for Visual Studio 2010, the Silverlight toolkit, and more.
And it's just as easy to add popular third-party web apps: DotNetNuke, WordPress, Drupal, Joomla!, phpBB and more. Or one of these tools, at least: check more boxes and an error message complains that "only one application is allowed per installation". Still, it's better than nothing.
Please note, the 84KB download is for Microsoft's Web Platform Installer only. Launch this, choose the components you want to install, and the installer will then let you know the total download size.