Password prompting in WinXP

I recently reinstalled XP in my pc, the first time i did i chose "New installation", so i selected the partition to install the os into, but this time i chose "Update" (from Win98) and i have notice some changes, one of them is what bring me here and ask.

Everytime my pc starts up, WinXP prompts me for the administrator password, i hava a blank pass, i mean there is no password, so i wonder where i can modify that in order the pc starts up automatically without asking me for the password.

Also, when i had the "New installation", i just disabled the hibarnate feature and my pc shuts down automatically, but now, i did the same but i receive the message "Now it's safe to turn off your computer", that i hate, why dont it shuts down automatically as b4? how can i fix that?

Any help will be welcomed. Thanks.

Control Panel --> User Settings maybe?
If you remove all other users apart from the common one and have no password, it should log on automatically.

If that doesnt work, look in local security policy