Hello parag,
Unfortunately there is not an easy answer to this.
You can adjust the core tables to add further data to the registration, but if you do this consider what will you do when you want to upgrade your installation of DNN? - It will cause you a major headache as you will have to re-apply all of those changes to the new install.
This is something I am currently pondering on for a current project.
The options I see available are to create a module especially for this.
Potentially you could create a page and add the account module to the page so that it displays the users details and then underneath this add a separate module which collects further details regarding the user. The problem will be tying together the details of the user ID with the extra details that you collect.
I would have a look around www.snowcovered.com to see if anyone has created a module which provides a solution, or the other option is to learn how to create a module. If you have not done this before then I would check out the series of videos at www.seaburydesign.com
X-Mod on snowcovered is a good module for collecting data, but i don't know if it will be suitable for your needs.
Otherwise I would suggest asking a question at:
http://forums.asp.net/90/ShowForum.aspx
I would be very interested in hearing the solution you opt for as this is something I also need to do.
- As further info, on a previous project I had to collect full company information for a recycling directory, the way I achieved this was to get the user to register with the website and create a username.
Once they had created a username they could access a private area of the website and create their company profile for the directory.
I could get away with this because I needed to collect several pages of information. This also gave me the flexibility to give different privaleges to different users - ie. recyclers get access to a private area to trade equipment, general users get access to the forum and can post tenders etc.
Hope this provides some starting points,