Abhijith:
skybox = content.Load<Skybox>(@"Content\Skyboxes\skybox2");
For the content.Load<Skybox>(..) you need the custom content processor so that XNA can recognize the type "Skybox".
Without seeing the content pipeline code or the article/tutorial you are using, I can't really tell you how to convert that to XNA 2.0, not on top of my mind ;)
So, please tell me:
1. What XNA version are you using? (I assume 2.0)
2. What article/tutorial are you following? (give a link to it)
With some more information I can try to help you.
Again, I can recommend that tutorial I linked to before - it is more simple than creating a custom model processor etc.