In IIS6 or below where on a folder you want to block any files that would normally be handled by a script processor such as asp.dll, you would open the properties dialog for that folder in IIS manager then on the directory tab under application settings you would change the combo-box next to "Execute Permission" and set it to "none".
How is this done on II7?
In IIS 7 this is included in the Handler Mappings section. On your site click the Handler Mappings Icon, then click the Edit Handler Permissions option in the actions menu.
1.Open IIS Manager and navigate to the level you want to manage. For information about opening IIS Manager, see Open IIS Manager (IIS 7). For information about navigating to locations in the UI, see Navigation in IIS Manager (IIS 7).
2.In Features View, on the server, site, or applicationHome page, double-click Handler Mappings.
3.In the Actions pane, click Edit Feature Permissions.
4.In the Edit Feature Permissions dialog box, do the following:
Select Read to enable handlers that require read access or clear Read to disable handlers that require read access to a virtual directory.
Select Scripts to enable handlers that require script rights or clear Scripts to disable handlers that require script rights in a virtual directory.
Select Execute to enable handlers that require execute rights or clear Execute to disable handlers that require execute rights in a virtual directory. The Execute option is enabled only when Scripts is selected.