Microsoft has released a free BETA version of the Web Platform Installer which corrals together all the free components you need for developing web applications on Windows Vista. To download the installer, go here: http://www.microsoft.com/web/channel/products/WebPlatformInstaller.aspx .
The first screen of the BETA installer lets you select Complete, ASP.NET Developer, or Your Choice:
If you select Your Choice and click Next, you can select just the options you want. You can also select a profile in the Recommendations list on the Web Server tab to distill the options down to the profile that fits your development the best, including ASP.NET Developer, PHP Developer, or Classic ASP Developer: