To solve this problem, you need to access IIS 7 Manager and make sure that the:
- Application Pool is switched from Default to Classic
- Logon User in Classic Application Pool is LocalSystem
- Enable for 32-bit applications
To enable 32 bit application for IIS. Right click on the Application Pool and select “Advanced Settings” then “Enable 32-bit Applications.”
Some other help can be found here and here.
To Open SiteFinity in Visual Studio 2008, go here.
Here is an installation guide and permissions