I m bit confused about the architecture used in dotnetnuke. I have read about dotnetnuke architecture and MVC architecture.  DNN uses MVC to build modules...Is there any difference between these architecures? R they both same?? Please differentiate if they r different.

Are you talking MVC as in what Catalyst (Perl) uses as an architecture?  What Microsoft refers to as Document/View (If I remember MFC well enough...)?  If so, that's not really what DNN uses, it's more like the new Ribbon in Office 2007.  Although DNN may eventually move that direction, it currently runs older, more basic technology with post backs, same basic technology from ASP.NET 1.0.

Though with ASP.NET 3.5 and VS 2008, development may move quicker to that type of architecture.  It's used a lot in the Java world now, I believe.

Jeff