A simple web application runs fine on internal web server, but the time we put it on IIS7 specially in Windows Vista, its start giving configuration error, first and foremost is issue with Modules.
This configuration section cannot be used at this path. This happens when the section is locked at a parent level. Locking is either by default (overrideModeDefault="Deny"), or set explicitly by a location tag with overrideMode="Deny" or the legacy allowOverride="false".
And its points to <handlers> section under <system.webServer> section. The issue related to IIS don’t have ASP.NET installed. You can check your Windows feature, although you have installed IIS7 and compatibility for IIS6, ASP.NET is not getting installed automatically. Here is the Windows feature should look like as in following image.
You can find this window from Control Panel –> Programs and Features –> Turn Windows features on or off [Left panel]
If you have ASP.NET installed on your IIS 7.0 then you have to change the configuration from applicationHost.config file, which resides in %windir%\system32\inetsrv\config\applicationHost.config. You can find the entry for handlers and it has value Deny for property overrideModeDefault, change it to Allow.
<section name="handlers" overrideModeDefault="Deny" /> to <section name="handlers" overrideModeDefault="Allow" />
While saving file I am pretty much sure that it asks for Administrator account although your role is Administrators as you are not owner of that file you can’t make change to file, so solution for this is login as Administrator and do the changes. For vista Administrator is not active for login so find my post which help you to login as Administrator.