If you are using MVC, it will require adding the MVC entries to the web.config. If you install MVC in your development environment and create the project as an MVC project, the file should already contain them:
<system.web>
<compilation debug="true" targetFramework="4.0">
<assemblies>
<add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
</assemblies>
</compilation>
<pages>
<namespaces>
<add namespace="System.Web.Mvc" />
<add namespace="System.Web.Mvc.Ajax" />
....
If you are developing on this box and it was upgraded from something with IIS 6 (Server 2000/2003?) to Win 7 and IIS 7 (which seems like a downgrade, except for the IIS version, to me), then you'd need to re-install MVC on this dev box. If this is the final server, all you should need is to publish the web.config, DLL file in the bin directory, and the views, any scripts, and CSS.