Dear Robox,
I tried the way which you explained. I created a new home page without 'user account' module by using 'Add Existing Module' option. I changed the home page option in Admin->Site Settings. When I go for my site, my new home page is displayed. Once I tried to login, it is redirected to 'Manage Profile' page. It is asking to 'update' or 'unregister'. Even after selecting the 'update' option, the page is not changing.
I have one more doubt which I suspect as the reason for my problem.
In Admin-->Security Roles-->User Settings, the 'Require a valid Profile for Login' check box is always selected. Even If I change it, it is not updating. I have seen the following comments at the top of the page.
"In this section you can review the membership provider's settings. Some providers may allow you to edit the settings. The default provider based on the ASP.NET MemberRole requires you to edit web.config, so the settings can not be updated here."
I am not a programmer. So that I dont know what to do. Is it the reason for my problem?
Please help me to sort out the problem.