got Hacked today :(

Hi guys, the feeling sucks i had 3 years woth of entries (400+) and the hacker deleted 3/4 of them! Below is my little story

Woke up early this morning to work on my essay, did the usual and surfed to my guestbook to remove the everyday 2-4 spam entries, but this time it waaas different!

The guestbook background was all whiite and the font size was ridiculously huuge! I was like hmmmmmm.....maybe my brother fiddled with the settings...so i go to phpmyadmin and notice that the admin username is no LONGER ME! all the fields have been changed, even the color settings.

The username is wsteam, his password is
*07836E0D063D978124FDBB1FD43B33869BD2462F
Email address: wsteam@5_yahooyahoo.com

allong with 5 new entries in the guestbook that are all blank, not even an IP address tagged (even in phpmyadmin).

Im feeling really depressed as i dont know what to do now, i cant even ban his ip address because obviously i dont know what it is. I had everything disabled HTML/IMAGING...and even removed the website fields.....i had the verification question installed too which killed lots of bots

anyways what should i do next? how do you think he punctured into my config?