Taken from TweakXP
1. Go to Control panel
2. Click administrative tools
3. Local Security Settings
4. Click Minimum password length
5. Reduce it to 0, No password required
6. Go to user account in control panel click your account and remove password
Here's another way:
goto control panel > user accounts > "change the way users log on or off" > uncheck the first box "Use the Welcome Screen".
Hope this helps.