When you unbox and start your android phone first time it will ask to enter your Gmail account details , this account is necessary to install apps from androidmarket ,mail ,contacts etc. if you want to reset firstly assigned Gmail account with your device then doing hard reset to phone will remove it and ask again for new Gmail account.
but problem is you will lose all your data stored in phone, so in this guide we are going to reset Gmail account on android without losing any data.
Instructions to Reset Google Account on Android Device
1. Enter to Menu > Setting > Application > Manage Application.
2. Navigate and click on Google Apps. Then click on “Clear Data” button.
3. When “All information you have saved in this application will be deleted permanently” message pop ups , Click on OK.
4. For more safety you can clean Data Cache in Mail. for cleaning cache Go to Settings > Applications > Manage Applications > Gmail.
5. Click on “Clear data” so that synchronization process in email will not give any error
6. Press on “Back” button. After that go to Home > Menu > Settings and tap on Data Synchronization
7 . Now You will see a new wizard appears asking to input Google Account information.
if your device not appeared in Google Apps when you do Manage Application.
To display it when you are in ‘Manage Application’, press on Menu then select Filter and select All or Running. after doing this you will see Google apps.