priyam,
While I'm sure it's possible to store blog posts and user details and what have you in an XML file... I wouldn't advise it. The more posts and replies and such that you end up with the larger the file will get and eventually it would reach a point where it would overwhelm system resources on your web host.
What you'd be looking for would be a database driven solution. Many hosting providers will give you a MySQL database for free (some even include an MSSQL database for free) which you can set up to contain all of your posts/replies/users/etc.
Calling information from a relational database is much less resource intensive than trying to locate information from an ever expanding flat file (like an XML file) and if you're using C#/ASP.Net for your code-behind the database connection and information management is very easily accomplished if you've had any training/education in how to code for those.
If, on the other hand, you are looking to use a 3rd party blog service to drive your site then you will need to check with those services as to the methods they require/recommend for connecting to and manipulating the data to/from their service (you had mentioned blogger/wordpress).
Hope this helps :twisted: Please remember to mark your thread solved once the issue is resolved.
