Here's a look at the options available from the IIS 7.0 Defaults Dialog page
In response to the comment by "Anonymous", ActivePERL is not from Microsoft, it is from a 3rd-party company named ActiveState (see www.activestate.com); Microsoft does not install any version of PERL.
Also - Microsoft's strategy is definitively not to "kill all other companies web software products"; in fact, with IIS 7 Microsoft tried to make the product easier for 3rd-party developers to develop applications for IIS than ever before. For example, Microsoft's adoption of FastCGI in IIS enables a variety of other dynamic programming technologies from other companies (e.g. PHP, PERL, etc.) If you were to take a look at the “Downloads” section on the www.iis.net web site, you would see that a growing community of 3rd-party developers is creating applications for IIS 7.
All of that being said - because of the introduction of the integrated pipeline in IIS 7, some legacy IIS 5 and IIS 6 applications might have some migration issues, but the detailed error messages in IIS 7 will list the problem and the possible migration resolutions. If you want to host your IIS 5 or IIS 6 application on IIS 7 and you don't want to migrate your application, you can run the application in an application pool that has been configured to use "Classic" mode.