How do I go about blocking the system so that no one else sharing my internet connection at home.?

Answer 1

If what you want to do is block others from using your internet connection, just encrypt it. If you want top keep your personal account secure from others, password protect your account.

Answer 2

Not really sure exactly what you're asking, but if you simply want to have other users at your home have access to the internet, but not have access to your "internet account", history, bookmarks, etc., then;
1. Set up separate identities for each user in your house
(Start/Control Panel/User Accounts)
2. In the same place, set up a password on your user account
3. Make sure you Log Off whenever you leave the computer.