If you make the startling decision that you don't need your Gmail account anymore, you can simply close the account. To do so, just follow these steps:
1. Click 'Settings' at the top of any Gmail page.
2. Click 'Account Settings.'
3. Click 'Delete Gmail Service' along the left side, under 'Delete Account.'
4. Enter all information into the appropriate fields, and check the box next to 'Yes, I want to remove Gmail from my account.'
5. Click 'Remove Gmail.'
Please keep in mind that once you close your Gmail account, you can't reactivate it, and you won't be able to retrieve any emails. After a certain period of time, Gmail recycles your username, so we can't guarantee that it will be available if you decide to open another Gmail account.
توضیحات خود سایت که به قدر کافی هم گویاست! اینم لینکش :
http://gmail.google.com/support/bin...y=delete+an+account&topic=0&type=f&ctx=search