Before you start make a note of the Usernames on your computer and that your account has Administration rights.

1. Open My Computer
2. Click on Control Panel in the 'Other places' panel to your left.
3. Open User Accounts
4. Then click Change the way users log on or log off.
5. And click on Use the Welcome Screen so the Tick is no longer visible.
6. Lastly click Apply Changes

I have only tested this on Windows XP Pro and so am uncertain if this will work on Home, although i'm sure Microsoft would not leave out such a simple feature to the Home edition.