I am new to DNN, I'm trying to install DNN 4. I have modified the web.config but when i try to run it http://localhost/dotnetnuke_2  i get following error

DotNetNuke Configuration Error

Object reference not set to an instance of an object.

DotNetNuke has extensive file upload capabilities for content, modules, and skins. These features require custom security settings so that the application is able to create and remove files in your website.

Using Windows Explorer, browse to the root folder of the website ( C:\DotNetNuke by default ). Right-click the folder and select Sharing and Security from the popup menu ( please note that if you are using Windows XP you may need to Enable Simple File Sharing before these options are displayed ). Select the Security tab. Add the appropriate User Account and set the Permissions.

If using Windows 2000 - IIS5
- the {Server}\ASPNET User Account must have Read, Write, and Change Control of the virtual root of your website

If using Windows 2003 - IIS6
- the NT AUTHORITY\NETWORK SERVICE User Account must have Read, Write, and Change Control of the virtual root of your website 

I have set all the permission/security...

Can someone please help !!!!!!!!!!!!!!!

dogar